Using virtual networking devices to connect managed computer networks

ABSTRACT

Techniques are described for providing managed virtual computer networks whose configured logical network topology may have one or more virtual networking devices, such as by a network-accessible configurable network service, with corresponding networking functionality provided for communications between multiple computing nodes of a virtual computer network by emulating functionality that would be provided by the networking devices if they were physically present. The networking functionality provided for a managed computer network may include supporting a connection between that managed computer network and other managed computer networks, such as via a provided virtual peering router to which each of the managed computer networks may connect, with the functionality of the virtual peering router being emulated by modules of the configurable network service without physically providing the virtual peering router, including to manage data communications between computing nodes of the inter-connected managed computer networks in accordance with client-specified configuration information.

BACKGROUND

Many companies and other organizations operate computer networks thatinterconnect numerous computing systems to support their operations,with the computing systems alternatively co-located (e.g., as part of aprivate local area network, or “LAN”) or instead located in multipledistinct geographical locations (e.g., connected via one or more otherprivate or shared intermediate networks). For example, data centershousing significant numbers of interconnected computing systems havebecome commonplace, such as private data centers that are operated byand on behalf of a single organization, as well as public data centersthat are operated by entities as businesses. Some public data centeroperators provide network access, power, and secure installationfacilities for hardware owned by various customers, while other publicdata center operators provide “full service” facilities that alsoinclude hardware resources made available for use by their customers.However, as the scale and scope of typical data centers and computernetworks has increased, the task of provisioning, administering, andmanaging the associated physical computing resources has becomeincreasingly complicated.

The advent of virtualization technologies for commodity hardware hasprovided some benefits with respect to managing large-scale computingresources for many customers with diverse needs, allowing variouscomputing resources to be efficiently and securely shared betweenmultiple customers. For example, virtualization technologies such asthose provided by VMWare, XEN, Linux's KVM (“Kernel-based VirtualMachine”), or User-Mode Linux may allow a single physical computingmachine to be shared among multiple users by providing each user withone or more virtual machines hosted by the single physical computingmachine, with each such virtual machine being a software simulationacting as a distinct logical computing system that provides users withthe illusion that they are the sole operators and administrators of agiven hardware computing resource, while also providing applicationisolation and security among the various virtual machines.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C are network diagrams illustrating example embodiments ofconfiguring and managing networking functionality provided for computingnodes belonging to a managed computer network.

FIGS. 2A-2F illustrate examples of managing communications betweencomputing nodes of a managed virtual overlay computer network.

FIG. 3 is a block diagram illustrating example computing systemssuitable for executing an embodiment of a system for managingcommunications between computing nodes.

FIG. 4 illustrates a flow diagram of an example embodiment of a CNSSystem Manager routine.

FIGS. 5A-5B illustrate a flow diagram of an example embodiment of a CNSCommunication Manager routine.

FIGS. 6A-6B illustrate a flow diagram of an example embodiment of a CNSNetwork Routing Manager routine.

DETAILED DESCRIPTION

Techniques are described for providing virtual networking functionalityfor managed computer networks, such as for computer networks that aremanaged for and provided on behalf of users or other entities. Suchmanaged computer networks may in some embodiments be provided by aconfigurable network service to users or other entities who arecustomers (e.g., for a fee) or otherwise clients of the configurablenetwork service, such as to remote clients that access the configurablenetwork service and/or the provided managed computer networks fromremote locations over one or more intervening networks. In at least someembodiments, the described techniques enable a user to configure orotherwise specify a network topology for a managed computer networkbeing provided for the user, such as to separate multiple computingnodes of the managed computer network into multiple logical sub-networksinterconnected by one or more specified networking devices, or tootherwise include one or more specified networking devices that are eachassociated with a specified group of the multiple computing nodes. Aftera network topology is specified for a managed computer network,networking functionality corresponding to the specified network topologymay be provided in various manners, such as by implementing the managedcomputer network as a virtual computer network overlaid on one or moreother computer networks, and by providing functionality corresponding tothe specified network topology without physically implementing at leastsome of the specified network topology. For example, the configurablenetwork service may in some embodiments handle communications betweencomputing nodes of a managed computer network in accordance with itsspecified network topology by emulating at least some types offunctionality that would be provided by virtual networking devices forthe managed computer network if they were physically present, butwithout physically providing those networking devices. Similarly, insome embodiments, routing-related communications that include routinginformation for the managed computer network and that are directed tothe specified networking devices may be managed without physicallyproviding the networking devices, such as by intercepting the routingcommunications and using the routing information to update the networktopology for the managed computer network. In at least some embodiments,some or all of the described techniques are automatically performed byembodiments of a Network Routing Manager (“NRM”) module and/or one ormore other modules, such as one or more NRM modules and multiplecommunication manager modules that are part of a network-accessibleconfigurable network service that provides configurable computernetworks to clients.

In some embodiments, the providing of networking functionality for amanaged computer network provided by a configurable network service to afirst client may include supporting connections between that managedcomputer network and one or more other managed computer networks thatare provided by the configurable network service, such as other managedcomputer networks that are provided to other clients. Suchinter-connections between managed computer networks may have variousforms and be used for various purposes. As one illustrative example, afirst client who has a managed computer network may use that managedcomputer network to provide a service that is available to others, suchas a service that provides information to others on a regular basis—ifso, other clients that also have managed computer networks may configuretheir managed computer networks to be inter-connected to the managedcomputer network of the first client in order to receive informationfrom the service via that inter-connection, such as optionally in auni-directional manner that prevents the other clients' managed computernetworks from transmitting information to the first client's managedcomputer network. As another illustrative example, multiple clients whoeach have a managed computer network from the configurable networkservice may elect to have their managed computer networks beinter-connected in a bi-directional manner so that a computing node ofany one of the managed computer networks may send at least some types ofcommunications to a computing node on any other of the managed computernetworks—such multiple clients may, for example, belong to multiplecompanies that operate as partners or affiliates. It will be appreciatedthat many other inter-connection configurations and uses may beprovided.

In order to support connections between multiple managed computernetworks, the configurable network service in at least some embodimentsprovides a virtual peering router device to which each of the multiplemanaged computer networks may logically connect, such as by theconfigurable network service performing operations to emulatefunctionality of the provided virtual peering router, or to otherwiseperform operations to support the inter-connections between the multiplemanaged computer networks without physically providing the virtualpeering router device. When one of the multiple managed computernetworks logically connects to the virtual peering router device,computing nodes of that newly connected managed computer network areable to send routing-related communications to the connected virtualpeering router device, such as to provide information about thecomputing nodes and associated routes of that managed computer network.If other managed computer networks are also logically connected to thevirtual peering router device, and the virtual peering router device isconfigured to enable the other managed computer networks to sendcommunications to the newly connected managed computer network, theconfigurable network service may further provide information to thoseother managed computer networks that includes at least some of therouting information for the newly connected managed computer network,such as via one or more routing communications that are sent to thoseother managed computer networks and that are spoofed so as to appear tobe from the virtual peering router device—accordingly, those othermanaged computer networks are then able to route communications to thenewly connected managed computer network via the virtual peering routerdevice. If the virtual peering router device is so configured, similarrouting information for those other managed computer networks may alsobe sent to the newly connected managed computer network, to similarlyallow the newly connected managed computer network to sendcommunications to those other managed computer networks via the virtualpeering router device. The virtual peering router device may be enabledto inter-communicate with managed computer networks in a variety ofmanners, including in some embodiments based on the Border GatewayProtocol (“BGP”). Additional details related to actions of theconfigurable network service in providing functionality to supportvirtual peering routers and inter-connections between managed computernetworks are included below.

As noted above, the described techniques enable a user or other entityto in at least some embodiments configure or otherwise specify one ormore networking devices for a managed computer network being provided onbehalf of the user or entity (e.g., virtual networking devices that arepart of a logical network topology for the managed computer network, butthat are not physically provided), and include performing variousautomated actions to support such specified networking devices (e.g.,intercepting routing communications directed to virtual networkingdevices, and using routing information in the routing communications invarious manners), including in embodiments in which the managed computernetwork is a virtual computer network. Before discussing some details ofproviding virtual networking functionality corresponding to suchspecified networking devices for a managed computer network, someaspects of such managed computer networks in at least some embodimentsare introduced.

In particular, a managed computer network between multiple computingnodes may be provided in various ways in various embodiments, such as inthe form of a virtual computer network that is created as an overlaynetwork using one or more intermediate physical networks that separatethe multiple computing nodes. In such embodiments, the intermediatephysical network(s) may be used as a substrate network on which theoverlay virtual computer network is provided, with messages and othercommunications between computing nodes of the overlay virtual computernetwork being passed over the intermediate physical network(s), but withthe computing nodes being unaware of the existence and use of theintermediate physical network(s) in at least some such embodiments. Forexample, the multiple computing nodes may each have a distinct physicalsubstrate network address that corresponds to a location of thecomputing node within the intermediate physical network(s), such as asubstrate IP (“Internet Protocol”) network address (e.g., an IP networkaddress that is specified in accordance with IPv4, or “Internet Protocolversion 4,” or in accordance with IPv6, or “Internet Protocol version6,” such as to reflect the networking protocol used by the intermediatephysical networks). In other embodiments, a substrate network on which avirtual computer network is overlaid may itself include or be composedof one or more other virtual computer networks, such as other virtualcomputer networks implemented by one or more third parties (e.g., by anoperator or provider of Internet or telecom infrastructure).

When computing nodes are selected to participate in a managed computernetwork that is a virtual computer network overlaid on a substratenetwork, each computing node of the managed virtual computer network mayalso be assigned one or more virtual network addresses for the virtualcomputer network that are unrelated to those computing nodes' substratenetwork addresses, such as from a range of virtual network addressesused for the managed virtual computer network—in at least someembodiments and situations, the managed virtual computer network beingprovided may further use a networking protocol that is different fromthe networking protocol used by the substrate network (e.g., with thevirtual computer network using the IPv4 networking protocol, and thesubstrate computer network using the IPv6 networking protocol). Thecomputing nodes of the virtual computer network inter-communicate usingthe virtual network addresses (e.g., by sending a communication toanother destination computing node by specifying that destinationcomputing node's virtual network address as the destination networkaddress for the communication), but the substrate network may beconfigured to route or otherwise forward communications based onsubstrate network addresses (e.g., by physical network router devicesand other physical networking devices of the substrate network). If so,the overlay virtual computer network may be implemented from the edge ofthe intermediate physical network(s), by modifying the communicationsthat enter the intermediate physical network(s) to use substrate networkaddresses that are based on the networking protocol of the substratenetwork, and by modifying the communications that leave the intermediatephysical network(s) to use virtual network addresses that are based onthe networking protocol of the virtual computer network. Additionaldetails related to the provision of such an overlay virtual computernetwork are included below.

In at least some embodiments, a network-accessible configurable networkservice (“CNS”) is available for use by customers, such as a CNSprovided by a corresponding CNS system that provides and manages overlayvirtual computer networks for remote customers (e.g., users and otherentities). Such a CNS service may, for example, provide and use numerouscomputing nodes that are in one or more geographical locations (e.g., inone or more data centers) and that are inter-connected via one or moreintermediate physical networks. The CNS system may use variouscommunication manager modules at the edge of the one or moreintermediate physical networks to manage communications for the variousoverlay virtual computer networks as they enter and leave theintermediate physical network(s), and may use one or more system managermodules to coordinate other operations of the CNS system. For example,to enable the communication manager modules to manage communications forthe overlay virtual computer networks being provided, the CNS system maytrack and use various information about the computing nodes of eachvirtual computer network being managed, such as to map the substratephysical network address of each such computing node to the one or moreoverlay virtual network addresses associated with the computing node.Such mapping and other information may be stored and propagated invarious manners in various embodiments, including centrally or in adistributed manner, as discussed in greater detail below.

Furthermore, in order to provide managed virtual computer networks tousers and other entities, the CNS system allows users and other entitiesto interact with the CNS system in at least some embodiments toconfigure a variety of types of information for virtual computernetworks that are provided by the CNS system on behalf of the users orother entities, and may track and use such configuration information aspart of providing those virtual computer networks. The configurationinformation for a particular managed virtual computer network havingmultiple computing nodes may include, for example, one or more of thefollowing non-exclusive list: a quantity of the multiple computing nodesto include as part of the virtual computer network; one or moreparticular computing nodes to include as part of the virtual computernetwork; a range or other group of multiple virtual network addresses toassociate with the multiple computing nodes of the virtual computernetwork; particular virtual network addresses to associate withparticular computing nodes or particular groups of related computingnodes; a type of at least some of the multiple computing nodes of thevirtual computer network, such as to reflect quantities and/or types ofcomputing resources to be included with or otherwise available to thecomputing nodes; a geographic location at which some or all of thecomputing nodes of the virtual computer network are to be located; etc.In addition, the configuration information for a virtual computernetwork may be specified by a user or other entity in various manners invarious embodiments, such as by an executing program of the user orother entity that interacts with an API (“application programminginterface”) provided by the CNS system for that purpose and/or by a userthat interactively uses a GUI (“graphical user interface”) provided bythe CNS system for that purpose.

FIG. 1A is a network diagram illustrating an example of anetwork-accessible service that provides client-configurable managedcomputer networks to clients. In particular, in this example, at leastsome of the managed computer networks may be virtual computer networks,such as virtual computer networks that are created and configured asnetwork extensions to existing remote private computer networks ofclients, although in other embodiments the managed computer networks mayhave other forms and/or be provided in other manners. After configuringsuch a managed computer network being provided by the network-accessibleservice, a user or other client of the network-accessible service mayinteract from one or more remote locations with the provided computernetwork, such as to execute programs on the computing nodes of theprovided computer network, to dynamically modify the provided computernetwork while it is in use, etc. In particular, in the illustratedexample of FIG. 1A, a configurable network service (“CNS”) 105 isavailable that provides functionality to clients (not shown) over one ormore public networks 100 (e.g., over the Internet) to enable the clientsto access and use managed computer networks provided to the clients bythe CNS 105, including to enable the remote clients to dynamicallymodify and extend the capabilities of their remote existing privatecomputer networks using cloud computing techniques over the publicnetwork 100. In addition, the CNS 105 may provide functionality toenable clients to specify logical network topology information for theirmanaged virtual computer networks, and if so provides correspondingnetworking functionality (e.g., under control of an NRM module of theCNS 105, such as one of the other modules 125), as described in greaterdetail later.

In the example of FIG. 1A, a number of clients interact over the publicnetwork 100 with a system manager module 110 of the CNS 105 to createand configure various managed computer networks 120 being provided bythe CNS 105, with at least some of the provided computer networks 120being private computer network extensions to remote existing clientprivate networks 130, and with at least some such of the providedcomputer network extensions 120 being configured to enable privateaccess from one or more corresponding client private networks 130 overthe public network 100 (e.g., via VPN connections established overinter-connections 100 a and 100 b, or via other types of private ornon-private inter-connections). In this example embodiment, the managermodule 110 assists in providing functionality of the CNS 105 to theremote clients, such as in conjunction with various optional othermodules 115 of the CNS 105 and optionally various computing nodes 125and/or networking devices (not shown) that are used by the CNS 105 toprovide the managed computer networks 120. In at least some embodiments,the CNS manager module 110 may execute on one or more computing systems(not shown) of the CNS 105, and may provide one or more APIs that enableremote computing systems to programmatically interact with the module110 to access some or all functionality of the CNS 105 on behalf ofclients (e.g., to create, configure, and/or initiate use of managedcomputer networks 120). In addition, in at least some embodiments,clients may instead manually interact with the module 110 (e.g., via aGUI provided by the module 110) to perform some or all such actions.

The public network 100 in FIG. 1A may be, for example, a publiclyaccessible network of linked networks, possibly operated by distinctparties, such as the Internet. The remote client private networks 130may each include one or more existing private networks, such as acorporate or other private network (e.g., home, university, etc.) thatis partially or wholly inaccessible to non-privileged users, and thatincludes computing systems and/or other networked devices (not shown) ofa client. In the illustrated example, the provided computer networks 120each include multiple computing nodes (not shown), at least some ofwhich may be from a plurality of optional computing nodes 125 providedby or otherwise under the control of the CNS 105, while in otherembodiments at least some other computing systems 135 may be used toprovide some or all computing nodes for one or more of the providedcomputer networks 120, such as other computing systems 135 that areprovided by or under control of the client for whom a computer network120 that uses those other computing systems 135 is provided, or othercomputing systems 135 that are provided by third parties (e.g., for afee). Each of the provided computer networks 120 may be configured invarious ways by the clients for whom they are provided, such as to be anextension to a corresponding remote computer network 130, and may eachbe a private computer network that is accessible only by the client thatcreates it, although in other embodiments at least some computernetworks provided by the CNS 105 for clients may be publicly accessibleand/or may be standalone computer networks that are not extensions toother existing computer networks 130. Similarly, while at least some ofthe provided computer networks 120 in the example may be extensions toremote client computer networks 130 that are private networks, in otherembodiments the provided computer networks 120 may be extensions toother client computer networks 130 that are not private networks.

Private access between a remote client private computer network 130 andcorresponding private computer network extension 120 provided for aclient may be enabled in various ways, such as by establishing a VPNconnection or other private connection between them that allowsintercommunication over the public network 100 in a private manner. Forexample, the CNS 105 may automatically perform appropriate configurationon its computing nodes and other computing systems to enable VPN accessto a particular private network extension 120 of a client, such as byautomatically configuring one or more VPN mechanisms hosted by the CNS105 (e.g., software and/or hardware VPN mechanisms), and/or mayautomatically provide appropriate configuration information to theclient (e.g., credentials, access points, and/or other parameters) toallow a VPN mechanism hosted on the remote client private network 130(e.g., a software VPN endpoint that is provided by one of the multiplecomputing nodes of the provided network extension 120) to establish theVPN access. After VPN access has been appropriately enabled and/orconfigured, a VPN connection may be established between the remoteclient private network and the provided private network extension, suchas initiated by the client using IPsec (“Internet Protocol Security”) orother appropriate communication technologies. For example, in someembodiments, a VPN connection or other private connection may beestablished to or between networks that use MPLS (“Multi Protocol LabelSwitching”) for data transmission, such as instead of an IPsec-based VPNconnection. In addition, in the illustrated example, variousnetwork-accessible remote resource services 140 may optionally beavailable to remote computing systems over the public network 100,including to computing nodes on the remote client private networks 130.The resource services 140 may provide various functionality to theremote computing nodes, such as for at least some of the resourceservices 140 to provide remote computing nodes with access to varioustypes of network-accessible computing-related resources. Furthermore, atleast some of the computer networks 120 that are provided by the CNS 105may be configured to provide access to at least some of the remoteresource services 140, with that provided access optionally appearing tocomputing nodes of the provided computer networks 120 as being locallyprovided via virtual connections 117 that are part of the providedcomputer networks 120, although the actual communications with theremote resource services 140 may occur over the public networks 100(e.g., via inter-connections 100 b and 100 c). In addition, in at leastsome embodiments, multiple distinct provided computer networks 120 maybe configured to enable inter-access with each other, as described ingreater detail elsewhere.

The provided computer networks 120 may each be configured by clients invarious manners. For example, in at least some embodiments, the CNS 105provides various computing nodes 125 that are available for use withcomputer networks provided to clients, such that each provided computernetwork 120 may include a client-configured quantity of multiple suchcomputing nodes that are dedicated for use as part of that providedcomputer network. In particular, a client may interact with the module110 to configure a quantity of computing nodes to initially be includedin a computer network provided for the client (e.g., via one or moreprogrammatic interactions with an API provided by the CNS 105). Inaddition, the CNS 105 may provide multiple different types of computingnodes in at least some embodiments, such as, for example, computingnodes with various performance characteristics (e.g., processor speed,memory available, storage available, etc.) and/or other capabilities. Ifso, in at least some such embodiments, a client may specify the types ofcomputing nodes to be included in a provided computer network for theclient. In addition, in at least some embodiments, a client may interactwith the module 110 to configure network addresses for a computernetwork provided for the client (e.g., via one or more programmaticinteractions with an API provided by the CNS 105), and network addressesmay later be dynamically added, removed or modified for a providedcomputer network of a client in at least some such embodiments, such asafter the provided computer network has already been in use by theclient. In addition, in at least some embodiments, a client may interactwith the module 110 to configure network topology information for acomputer network provided for the client (e.g., via one or moreprogrammatic interactions with an API provided by the CNS 105), and suchnetwork topology information may later be dynamically modified for aprovided computer network in at least some such embodiments, such asafter the provided computer network has already been in use by theclient. Furthermore, in at least some embodiments, a client may interactwith the module 110 to configure various network access constraintinformation for a computer network provided for the client (e.g., viaone or more programmatic interactions with an API provided by the CNS105), and such network access constraint information may later bedynamically modified for a provided computer network in at least somesuch embodiments, such as after the provided computer network hasalready been in use by the client.

Network addresses may be configured for a provided computer network invarious manners in various embodiments. For example, if a particularprovided computer network that is being configured is an extension to anexisting remote client computer network, the client may specify one ormore address ranges (e.g., a Classless Inter-Domain Routing (“CIDR”)address block) or other groups of network addresses for the providedcomputer network that are a subset of the network addresses used by theexisting remote client computer network, such that at least some of thespecified network addresses are used for the computing nodes of theprovided computer network. Such configured network addresses may in somesituations be virtual or private network addresses that are not directlyaddressable from computing systems on the public network 100 (e.g., ifthe existing remote client computer network and the correspondingprovided network extension use network address translation techniquesand/or virtual networking techniques for the client computer network andits provided network extension), while in other situations at least someof the configured network addresses may be public network addresses thatare directly addressable from computing systems on the public network100 (e.g., a public network address that is a static Internet-routableIP address or other non-changing network address). In other embodiments,the CNS 105 may automatically select network addresses to be used for atleast some computing nodes of at least some provided computer networks,such as based on network addresses that are available for use by the CNS105, based on selecting network addresses that are related to networkaddresses used by remote existing computer networks corresponding to theprovided computer networks, etc. Furthermore, if two or more of thecomputer networks provided by the CNS 105 are configured to enableinter-communications between the provided computer networks (e.g., fortwo or more computer networks provided to a single customer, such as fordifferent departments or groups within a single organization; for two ormore computer networks provided to two or more distinct customers;etc.), the CNS 105 may in some embodiments automatically select networkaddresses to be used for at least some computing nodes of those providedcomputer networks to facilitate the inter-communications, such as byusing different network addresses for the various provided computernetworks. In addition, in at least some embodiments in which the CNS 105provides virtual networks to clients, such as by using overlay networkson a substrate network, each client may be allowed to specify anynetwork addresses to be used for their provided computer networks, evenif multiple clients specify the same or overlapping network addressesfor their respective provided computer networks—in such embodiments, theCNS 105 manages the network addresses distinctly for each client, suchthat a first client may have a first computing node associated with aparticular specified network address for the first client's providedcomputer network, while a distinct second client may have a distinctsecond computing node associated with the same particular specifiednetwork address for the second client's provided computer network. Oncenetwork addresses are configured or otherwise determined for a providedcomputer network, the CNS 105 may assign the network addresses tovarious of the computing nodes selected for the provided computernetwork, such as in a random manner, by using DHCP (“Dynamic HostConfiguration Protocol”) or other techniques for dynamic assignment ofnetwork addresses, etc.

Network topology information may be configured for a provided computernetwork in various manners in various embodiments. For example, a clientmay specify particular types of networking devices (e.g., routers,switches, etc.) and/or other network devices or nodes (e.g., loadbalancers, firewalls, proxies, network storage devices, printers, etc.)to be part of the provided computer network, and may specifyinterconnectivity information between networking devices and computingnodes. Furthermore, in at least some embodiments, the CNS 105 mayprovide available computing nodes in multiple geographical locations(e.g., in multiple geographically distributed data centers), and theconfiguration information specified by a client for a provided computernetwork may further indicate one or more geographical locations in whichcomputing nodes of the provided computer network are to be located(e.g., to provide fault tolerance among the computing nodes of aprovided computer network by having them located in multiplegeographical locations), and/or may otherwise provide information aboutpreferences or requirements of how the computing nodes of the providedcomputer network are to interoperate that is used by the CNS 105 toselect one or more such geographical locations (e.g., minimum or maximumnetwork latency or bandwidth for computing node intercommunications;minimum or maximum network proximity between computing nodes; minimum ormaximum geographic proximity between computing nodes; having localaccess to particular resources or functionality that is not available inall such geographic locations; having specified locations relative toother external computing systems, such as to a remote computer networkof the client and/or to a remote resource service; constraints or otherpreferences based on the cost of obtaining use of particular computingnodes and/or for particular types of interactions with particularcomputing nodes, such as costs associated with providing data to and/orfrom those computing nodes; etc.). As discussed in greater detailelsewhere, in at least some embodiments, the inter-connections andintercommunications between computing nodes of a provided computernetwork are managed using an underlying substrate network of the CNS105, and if so, some or all of the configured network topologyinformation may be simulated or otherwise emulated in at least some suchembodiments using the underlying substrate network and correspondingmodules of the CNS 105. For example, each of the computing nodesprovided by the CNS 105 may be associated with a node communicationmanager module of the CNS 105 that manages communications to and fromits associated computing node(s), and if so, the associatedcommunication manager module for a computing node may take variousactions to emulate desired functionality of a network with respect tothat computing node, as discussed in greater detail elsewhere.

Network access constraint information may also be configured for aprovided computer network in various manners in various embodiments. Forexample, a client may specify information about whether and how some orall of the computing nodes of a provided computer network are allowed tocommunicate with other computing nodes of the provided computer networkand/or with other external computing systems, such as based on one ormore of the following: directions of communications (incoming versusoutgoing); types of communications (e.g., based on the types of contentincluded and/or the types of communication protocols used, such as toallow HTTP requests for text but not images and to not allow FTPrequests); locations of other computing systems (e.g., whether part ofthe provided computer network, part of a remote client computer networkcorresponding to the provided computer network, part of a remoteresource service to which access has been established, external to theprovided computer network and any corresponding remote client computernetwork, etc.); types of other computing systems; etc. In a mannersimilar to that for network topology information, the CNS 105 mayenforce network access constraint information for provided computernetworks in various manners.

Thus, managed computer networks may be provided for clients in variousmanners in various embodiments, and may be configured to have varioustypes of functionality in various embodiments.

In addition, in at least some embodiments, the computing nodes of themanaged computer networks may be physical computing systems and/or maybe virtual machines that are each hosted on one or more physicalcomputing systems, and the communications that are handled for managedcomputer networks may include transmissions of data (e.g., messages,packets, frames, streams, etc.) in various formats. As previously noted,some or all computing nodes used for a particular provided overlayvirtual computer network may in some embodiments be provided by the CNSsystem for use by users, while in other embodiments some or all suchcomputing nodes may instead be provided by a user who uses thosecomputing nodes. Furthermore, in at least some situations, an embodimentof the CNS system may be part of or otherwise affiliated with a programexecution service (or “PES”) that executes multiple programs on behalfof multiple customers or other users of the service, such as a programexecution service that uses multiple computing systems on multiplephysical networks (e.g., multiple physical computing systems andnetworks within a data center). In at least some such embodiments,virtual computer networks to which computing nodes belong may beselected based on associated users, such as based on the computing nodesexecuting programs on behalf of a user or other entity.

As previously noted, a virtual computer network may in some embodimentsbe provided as an overlay network that uses one or more intermediatephysical networks as a substrate network, and one or more such overlayvirtual computer networks may be implemented over the substrate networkin various ways in various embodiments. For example, in at least someembodiments, communications between nodes of an overlay virtual computernetwork are managed by sending those communications over the substratenetwork without encapsulating the communications, such as by embeddingvirtual network address information for a computing node of the virtualcomputer network (e.g., the destination computing node's virtual networkaddress) in a larger physical network address space used for anetworking protocol of the one or more intermediate physical networks.As one illustrative example, a virtual computer network may beimplemented using 32-bit IPv4 network addresses, and those 32-bitvirtual network addresses may be embedded as part of 128-bit IPv6network addresses used by the one or more intermediate physicalnetworks, such as by re-headering communication packets or other datatransmissions (e.g., using Stateless IP/ICMP Translation, or SIIT), orotherwise modifying such data transmissions to translate them from afirst networking protocol for which they are configured to a distinctsecond networking protocol. As another illustrative example, both thevirtual computer network and substrate computer network may beimplemented using the same network addressing protocol (e.g., IPv4 orIPv6), and data transmissions sent via the provided overlay virtualcomputer network using virtual network addresses may be modified to usedifferent physical network addresses corresponding to the substratenetwork while the transmissions are sent over the substrate network, butwith the original virtual network addresses being stored in the modifieddata transmissions or otherwise tracked so that the data transmissionsmay be restored to their original form when they exit the substratenetwork. In other embodiments, at least some of the overlay computernetworks may be implemented using encapsulation of communications.Additional details related to SIIT are available at “Request ForComments 2765—Stateless IP/ICMP Translation Algorithm”, February 2000,at tools<dot>ietf<dot>org<slash>html<slash>rfc2765 (where <dot> and<slash> are replaced by the corresponding characters with those names),which is hereby incorporated by reference in its entirety. Moregenerally, in some embodiments when implementing a first overlay networkusing a second substrate network, an N-bit network address that isspecified for the first overlay network in accordance with a firstnetwork addressing protocol may be embedded as part of another M-bitnetwork address that is specified for the second substrate network inaccordance with a second network addressing protocol, with “N” and “M”being any integers that correspond to network addressing protocols. Inaddition, in at least some embodiments, an N-bit network address may beembedded in another network address using more or less than N bits ofthe other network address, such as if a group of N-bit network addressesof interest may be represented using a smaller number of bits (e.g.,with L-bit labels or identifiers being mapped to particular N-bitnetwork addresses and embedded in the other network addresses, where “L”is less than “N”).

Various benefits may be obtained from embedding virtual network addressinformation in substrate network addresses for an underlying substratenetwork, including enabling an overlay of the virtual computer networkon the substrate network without encapsulating communications orconfiguring physical networking devices of the substrate network, asdiscussed in greater detail below. Furthermore, other information maysimilarly be embedded in the larger physical network address space for acommunication between computing nodes in at least some embodiments andsituations, such as an identifier specific to a particular virtualcomputer network that includes those computing nodes (e.g., a virtualcomputer network for a user or other entity on whose behalf thosecomputing nodes operate), an identifier corresponding to a particularvirtual local area network, etc. Additional details related to provisionof such virtual computer networks via use of overlay networks areincluded below.

Furthermore, in addition to managing configured network topologies forprovided virtual computer networks, the CNS system may use the describedtechniques to provide various other benefits in various situations, suchas limiting communications to and/or from computing nodes of aparticular virtual computer network to other computing nodes that belongto that virtual computer network. In this manner, computing nodes thatbelong to multiple virtual computer networks may share parts of one ormore intermediate physical networks, while still maintaining networkisolation for computing nodes of a particular virtual computer network.In addition, the use of the described techniques also allows computingnodes to easily be added to and/or removed from a virtual computernetwork, such as to allow a user to dynamically modify the size of avirtual computer network (e.g., to dynamically modify the quantity ofcomputing nodes to reflect an amount of current need for more or lesscomputing resources). Furthermore, the use of the described techniquesalso supports changes to an underlying substrate network—for example, ifthe underlying substrate network is expanded to include additionalcomputing nodes at additional geographical locations, existing or newvirtual computer networks being provided may seamlessly use thoseadditional computing nodes, since the underlying substrate network willroute communications to and from the substrate network addresses forthose additional computing nodes in the same manner as for otherpreviously existing substrate network computing nodes. In at least someembodiments, the underlying substrate network may be of any size (e.g.,spanning multiple countries or continents), without regard to networklatency between computing nodes at different locations.

At least some such benefits may similarly apply for logical sub-networks(or “subnets”) that are specified for such a particular provided virtualcomputer network, with the substrate network functionality used toemulate various functionality corresponding to the specified logicalsubnets. For example, the use of the underlying substrate network mayenable different computing nodes assigned to a particular logical subnetto be located at any position within the substrate network, with thesubstrate network forwarding communications to destination computingnodes based on those destination computing nodes' substrate networkaddresses. As such, the substrate network may support any specifiedlogical subnets, without any configuration regarding such specifiedlogical subnets and without any other use of information about suchspecified logical subnets, and with the CNS system modules (e.g.,communication manager modules) instead managing the correspondingfunctionality from the logical edges of the substrate network where theCNS system modules connect to the substrate network. In addition,modules of the CNS system may similarly operate to limit communicationswithin a particular provided virtual computer network to occur onlybetween computing nodes assigned to particular logical subnets specifiedfor the provided computer network, if so configured, such as byauthorizing whether to forward particular communications to indicateddestination computing nodes and by directing communications toparticular computing nodes selected to act as destination computingnodes, so as to provide network isolation for computing nodes assignedto those specified logical subnets.

For illustrative purposes, some embodiments are described below in whichspecific types of computing nodes, networks, communications, networktopologies, and configuration operations are performed. These examplesare provided for illustrative purposes and are simplified for the sakeof brevity, and the inventive techniques may be used in a wide varietyof other situations, some of which are discussed below.

FIG. 1B is a network diagram illustrating an example embodiment ofconfiguring and managing communications between computing nodesbelonging to a virtual computer network, by overlaying the virtualcomputer network and the communications on one or more intermediatephysical networks in a manner transparent to the computing nodes of thevirtual computer network. In this example, the configuring and managingof the communications is facilitated by a system manager module, anetwork routing manager module, and multiple communication managermodules of an example embodiment of the CNS system. The example CNSsystem may be used, for example, in conjunction with a publiclyaccessible program execution service (not shown), or instead may be usedin other situations, such as with any use of virtual computer networkson behalf of one or more entities (e.g., to support multiple virtualcomputer networks for different parts of a business or otherorganization on a private network of the organization).

The illustrated example includes an example data center 190 withmultiple physical computing systems operated on behalf of the CNSsystem. The example data center 190 is connected to an internet 185external to the data center 190, which provides access to one or morecomputing systems 145 a via private network 165, to one or more otherglobally accessible data centers 160 that each have multiple computingsystems (not shown), and to one or more other computing systems 145 b.The internet 185 may be, for example, a publicly accessible network ofnetworks (possibly operated by various distinct parties), such as theInternet, and the private network 165 may be, for example, a corporatenetwork that is wholly or partially inaccessible from computing systemsexternal to the private network 165. Computing systems 145 b may be, forexample, home computing systems or mobile computing devices that eachconnects directly to the Internet (e.g., via a telephone line, cablemodem, a Digital Subscriber Line (“DSL”), cellular network or otherwireless connection, etc.).

The example data center 190 includes a number of physical computingsystems 106 a-106 d and 155 a-155 n, as well as a Communication Managermodule 150 that executes on one or more other computing systems ordevices (not shown) to manage communications for the associatedcomputing systems 155 a-155 n, an external Communication Manager module108 that executes on one or more other computing systems or devices (notshown) to manage external communications that pass in and out of thedata center 190 over the Internet 185, a System Manager module 110 thatexecutes on one or more computing systems (not shown), and a NetworkRouting Manager module 170 that executes on one or more computingsystems (not shown). While not illustrated here, in some embodiments oneor more other modules may also be present and executing on one or morecomputing systems or devices of the data center 190, and the SystemManager module 110 and/or the Network Routing Manager module 170 mayhave one or more associated Communication Manager modules that manageinformation sent to and from the modules 110 and 170. In this example,each physical computing system 106 a-106 d hosts multiple virtualmachine computing nodes and includes an associated virtual machine(“VM”) communication manager module (e.g., as part of a virtual machinehypervisor monitor for the physical computing system), such as VMCommunication Manager module 109 a and multiple virtual machines 107 aon host computing system 106 a, and such as VM Communication Managermodule 109 d and multiple virtual machines 107 d on host computingsystem 106 d. Physical computing systems 155 a-155 n do not execute anyvirtual machines in this example, and thus may each act as a computingnode that directly executes one or more software programs on behalf of auser. The Communication Manager module 150 that manages communicationsfor the associated computing systems 155 a-155 n may be implemented aspart of various types of devices, such as, for example, a proxycomputing device, a firewall device, or a networking device (e.g., aswitch, router, hub, etc.) through which communications to and from thephysical computing systems travel. Similarly, the Communication Managermodule 108 that manages communications between the data center 190 andthe internet 185 may be implemented as part of various types of devices,such as, for example, a firewall device, a network address translation(“NAT”) device, one or more load balancer devices, the edge router 127c, or another networking device. In other embodiments, all or none ofthe physical computing systems at the data center may host virtualmachines.

This example data center 190 further includes multiple physicalnetworking devices, such as switches 119 a-119 b, edge router devices127 a-127 c, and core router devices 132 a-132 c. Switch 119 a is partof a physical sub-network that includes physical computing systems 106a-106 c, and is connected to edge router 127 a. Switch 119 b is part ofa distinct physical sub-network that includes physical computing systems106 d and 155 a-155 n, as well as the computing systems providing theCommunication Manager module 150, the System Manager module 110, and theNetwork Routing Manager module 170, and is connected to edge router 127b. The physical sub-networks established by switches 119 a-119 b, inturn, are connected to each other and other networks (e.g., the internet185) via an intermediate inter-connection network 122, which includesthe edge routers 127 a-127 c and the core routers 132 a-132 c. The edgerouters 127 a-127 c provide gateways between two or more physicalsub-networks or networks. For example, edge router 127 a provides agateway between the physical sub-network established by switch 119 a andthe inter-connection network 122, while edge router 127 c provides agateway between the inter-connection network 122 and internet 185 (e.g.,via the module 108). The core routers 132 a-132 c manage communicationswithin the inter-connection network 122, such as by routing or otherwiseforwarding packets or other data transmissions as appropriate based oncharacteristics of such data transmissions (e.g., header informationincluding source and/or destination addresses, protocol identifiers,etc.) and/or the characteristics of the inter-connection network 122itself (e.g., routes based on the physical network topology, etc.).

The illustrated System Manager module and Communication Manager modulesmay perform at least some of the described techniques in order toconfigure, authorize and otherwise manage communications sent to andfrom associated computing nodes, including to support providing variousvirtual networking functionality for one or more virtual computernetworks that are provided using various of the computing nodes, and/orto support providing various emulated functionality for one or morevirtual networking devices that are configured for one or more suchprovided virtual computer networks. Such functionality may further besupported in at least some embodiments by one or more Network RoutingManager modules, such as Network Routing Manager module 170, whichassist in determining and configuring routing information to be used tosupport provided virtual computer networks, as discussed in greaterdetail below. For example, Communication Manager module 109 a managesassociated virtual machine computing nodes 107 a, Communication Managermodule 109 d manages associated virtual machine computing nodes 107 d,and each of the other Communication Manager modules 109 and 150 maysimilarly manage communications for a group of one or more otherassociated computing nodes. The illustrated Communication Managermodules may configure communications between computing nodes so as tooverlay one or more particular virtual networks over one or moreintermediate physical networks that are used as a substrate network,such as over the inter-connection network 122, and so as to support oneor more virtual networking devices for such an overlaid particularvirtual network that are not physically provided. Furthermore, aparticular virtual computer network may optionally be extended beyondthe data center 190 in some embodiments, such as if one or more otherdata centers 160 also provide computing nodes that are available for useby the example CNS system, and the particular virtual network includescomputing nodes at two or more such data centers at two or more distinctgeographical locations. Multiple such data centers or other geographicallocations of one or more computing nodes may be inter-connected invarious manners, including the following: directly via one or morepublic networks in a non-private manner, or via a private connection,not shown (e.g., a dedicated physical connection that is not shared withany third parties, such as a leased line; a VPN or other mechanism thatprovides the private connection over a public network; etc.). Inaddition, while not illustrated here, other such data centers or othergeographical locations may each include one or more other CommunicationManager modules that manage communications for computing systems at thatdata center or other geographical location, such as CommunicationManager modules similar to module 108 that manage externalcommunications for their data centers.

In addition, a particular virtual computer network may optionally beextended beyond the data center 190 in other manners in otherembodiments, such as based on one or more other Communication Managermodules external to the data center 190 (e.g., if another CommunicationManager module is made part of private network 165, so as to managecommunications for computing systems 145 a over the Internet 185 andprivate network 165; etc.). Thus, for example, if an organizationoperating private network 165 desires to virtually extend its privatecomputer network 165 to one or more of the computing nodes of the datacenter 190, it may do so by implementing one or more CommunicationManager modules as part of the private network 165 (e.g., as part of theinterface between the private network 165 and the internet 185)—in thismanner, computing systems 145 a within the private network 165 maycommunicate with those data center computing nodes as if those datacenter computing nodes were part of the private network. In otherembodiments, the private computer network 165 may instead be extended toone or more computing nodes of the data center 190 by the module 108 ofthe data center 190 managing the communications between computing nodesof the private network 165 and particular data center 190 computingnodes.

Thus, as one illustrative example, one of the virtual machine computingnodes 107 a on computing system 106 a (in this example, virtual machinecomputing node 107 a 1) may be part of the same provided virtualcomputer network as one of the virtual machine computing nodes 107 d oncomputing system 106 d (in this example, virtual machine computing node107 d 1), and may further both be assigned to a specified logical subnetof that virtual computer network that includes a subset of the computingnodes for that virtual computer network, such as with the IPv4networking protocol being used to represent the virtual networkaddresses for the virtual computer network. The virtual machine 107 a 1may then direct an outgoing communication (not shown) to the destinationvirtual machine computing node 107 d 1, such as by specifying a virtualnetwork address for that destination virtual machine computing node(e.g., a virtual network address that is unique for the local broadcastdomain of the specified subnet). The Communication Manager module 109 areceives the outgoing communication, and in at least some embodimentsdetermines whether to authorize the sending of the outgoingcommunication, such as based on previously obtained information aboutthe sending virtual machine computing node 107 a 1 and/or about thedestination virtual machine computing node 107 d 1 (e.g., informationabout virtual computer networks and/or entities with which the computingnodes are associated, information about any specified logical subnets towhich the computing nodes belong, etc.), and/or by dynamicallyinteracting with the System Manager module 110 (e.g., to obtain anauthorization determination, to obtain some or all such information,etc.). By not delivering unauthorized communications to computing nodes,network isolation and security of entities' virtual computer networks isenhanced.

If the Communication Manager module 109 a determines that the outgoingcommunication is authorized (or does not perform such an authorizationdetermination), the module 109 a determines the actual physical networklocation corresponding to the destination virtual network address forthe communication. For example, the Communication Manager module 109 amay determine the actual destination network address to use for thevirtual network address of the destination virtual machine 107 d 1 bydynamically interacting with the System Manager module 110, or may havepreviously determined and stored that information (e.g., in response toa request from the sending virtual machine 107 a 1 for information aboutthat destination virtual network address, such as a request that thevirtual machine 107 a 1 specifies using Address Resolution Protocol, orARP). The Communication Manager module 109 a then re-headers orotherwise modifies the outgoing communication so that it is directed toCommunication Manager module 109 d using an actual substrate networkaddress, such as if Communication Manager module 109 d is associatedwith a range of multiple such actual substrate network addresses. FIGS.2A-2F provide examples of doing such communication management in someembodiments, including to emulate functionality corresponding to one ormore virtual networking devices specified for the virtual network thatare not physically provided.

When Communication Manager module 109 d receives the communication viathe inter-connection network 122 in this example, it obtains the virtualdestination network address for the communication (e.g., by extractingthe virtual destination network address from the communication), anddetermines to which of the virtual machine computing nodes 107 d managedby the Communication Manager module 109 d that the communication isdirected. The Communication Manager module 109 d next determines whetherthe communication is authorized for the destination virtual machinecomputing node 107 d 1, with examples of such authorization activitiesdiscussed in further detail in the examples of FIGS. 2A-2F. If thecommunication is determined to be authorized (or the CommunicationManager module 109 d does not perform such an authorizationdetermination), the Communication Manager module 109 d then re-headersor otherwise modifies the incoming communication so that it is directedto the destination virtual machine computing node 107 d 1 using anappropriate virtual network address for the virtual computer network,such as by using the sending virtual machine computing node 107 a 1'svirtual network address as the source network address and by using thedestination virtual machine computing node 107 d 1's virtual networkaddress as the destination network address. The Communication Managermodule 109 d then forwards the modified communication to the destinationvirtual machine computing node 107 d 1. In at least some embodiments,before forwarding the incoming communication to the destination virtualmachine, the Communication Manager module 109 d may also performadditional steps related to security, as discussed in greater detailelsewhere.

In addition, while not illustrated in FIG. 1B, in some embodiments thevarious Communication Manager modules may take further actions toprovide virtual networking functionality corresponding to a specifiednetwork topology for the provided virtual computer network (e.g., forone or more virtual networking devices for the provided virtual computernetwork), such as by managing communications between computing nodes ofthe provided virtual computer network in specified manners and byresponding to other types of requests sent by computing nodes of thevirtual computer network. For example, although being separated fromcomputing node 107 a 1 on physical computing system 106 a by theinter-connection network 122 in the example embodiment of FIG. 1B,virtual machine computing node 107 d 1 on physical computing system 106d may be configured to be part of the same logical sub-network of thevirtual computer network as computing node 107 a 1 (e.g., to not beseparated by any specified router devices). Conversely, despite thephysical proximity of virtual machine computing node 107 c 1 on physicalcomputing system 106 c to virtual machine computing node 107 a 1 onphysical computing system 106 a (i.e., being part of the same physicalsub-network without any intervening physical router devices) in theexample embodiment of FIG. 1B, computing node 107 c 1 may be configuredto be part of a distinct logical sub-network of the virtual computernetwork from that of computing node 107 a 1 (e.g., may be configured tobe separated by one or more specified router devices, not shown, whichin this example are virtual router devices that are not physicallyprovided for the virtual computer network). If computing nodes 107 a 1and 107 d 1 are configured to be part of the same logical sub-network,the previous example of sending a communication from computing node 107a 1 to computing node 107 d 1 may be performed in the manner previouslydescribed, without emulating the actions of any intervening virtualrouter devices (despite the use of multiple physical router devices inthe substrate inter-connection network 122 for forwarding thecommunication), since computing nodes 107 a 1 and 107 d 1 are configuredto be part of single sub-network in the specified network topology.

However, if computing node 107 a 1 sends an additional communication tocomputing node 107 c 1, the Communication Manager modules 109 a and/or109 c on the host computing systems 106 a and 106 c may performadditional actions that correspond to one or more virtual specifiedrouter devices configured in the specified network topology to separatethe computing nodes 107 a 1 and 107 c 1. For example, the sourcecomputing node 107 a 1 may send the additional communication in such amanner as to initially direct it to a first of the virtual specifiedrouter devices that is configured to be local to computing node 107 a 1(e.g., by including a virtual hardware address in the header of theadditional communication that corresponds to that first virtualspecified router device), with that first virtual specified routerdevice being expected to forward the additional communication on towardthe destination computing node 107 c 1 via the specified logical networktopology. If so, the source Communication Manager module 109 a maydetect that forwarding of the additional communication to the virtualfirst router device (e.g., based on the virtual hardware address used inthe header of the additional communication), or otherwise be aware ofthe configured network topology for the virtual computer network, andmay take actions to emulate functionality of some or all of the virtualspecified router devices that are configured in the specified networktopology to separate the computing nodes 107 a 1 and 107 c 1. Forexample, each virtual router device that forwards the additionalcommunication may be expected to take actions such as modifying a TTL(“time to live”) hop value for the communication, modify a virtualdestination hardware address that is specified for the communication toindicate the next intended destination of the additional communicationon a route to the destination computing node, and/or otherwise modifythe communication header. If so, the source Communication Manager module109 a may perform some or all of those actions before forwarding theadditional communication directly to the destination CommunicationManager module 109 c over the substrate network (in this case, viaphysical switch device 119 a) for provision to destination computingnode 107 c 1. Alternatively, some or all such additional actions toprovide the virtual networking functionality for the sent additionalcommunication may instead be performed by the destination CommunicationManager module 109 c after the additional communication is forwarded tothe Communication Manager module 109 c by the Communication Managermodule 109 a.

By providing virtual networking functionality using the describedtechniques, the CNS system provides various benefits. For example,because the various Communication Manager modules manage the overlayvirtual network and may emulate functionality of virtual networkingdevices, specified networking devices and other network topology do notneed to be physically implemented for virtual computer networks beingprovided, and thus corresponding modifications are not needed to theinter-connection network 122 or switches 119 a-119 b to supportparticular configured network topologies. Nonetheless, if the computingnodes and software programs of a virtual computer network have beenconfigured to expect a particular network topology for the providedvirtual computer network, the appearance and functionality of thatnetwork topology may nonetheless be transparently provided for thosecomputing nodes by the described techniques.

In addition, as previously noted, the described techniques includeperforming various additional actions in at least some embodiments tosupport networking devices specified for managed computer networks, suchas for virtual networking devices that are not physically provided andwhose functionality is emulated, with the modules of a configurablenetwork service being configured to perform various automated operationsto support such emulated functionality.

In particular, in at least some embodiments in which anetwork-accessible configurable network service supports virtualnetworking devices that are not physically provided for managed computernetworks, the configurable network service may perform various actionsto enable the virtual networking devices to participate in routingprotocols in the same manner or a similar manner as would an actualphysically provided networking device of the managed computer network.Such routing protocols generally enable network routers and othernetworking devices of a computer network, as well as other computingnodes that provide functionality to facilitate handling communicationsfor the computer network, to communicate with each other and exchangevarious types of routing information, so that network topology andoptionally network operation characteristics may be shared and usedthroughout the computer network. For example, some routing protocolsdetermine best paths to destinations based on the minimum number of hopsor on some other minimum distance measure, and exchange routinginformation that may include routing tables indicating a total distance“cost” and next best hop for each known destination—thus, a networkrouter that receives such routing table information may update its ownrouting table if the received routing information includes any “better”(i.e., lower cost) routes to known destinations, as well as to addinformation for any previously unknown destinations. Other routingprotocols determine best paths to destinations based on various costmeasures that are not limited to minimum distance, such as to instead oralso consider information such as actual network bandwidth, latency,reliability, load, etc.)—such other routing protocols may exchangerouting information that includes connectivity-related information(e.g., who are a sending router's nearest neighbors) and optionallynetwork operation characteristics information. A network router thatreceives such connectivity-related information may use it to optionallyupdate its map of the connectivity of the various routers in thenetwork, which it may then use to calculate the current best paths fromitself to the various destinations. The types of destinations that arouting protocol may represent when using such cost information or otherinformation may include, for example, a range of IP addresses (e.g.,IPv4 addresses, IPv6 addresses, etc.) that are represented by an IPaddress prefix, or instead one or more network addresses that arerepresented in another form (e.g., using MPLS labels). Typically, eachrouter will generate a subset of the set of total routing information(also referred to as a “routing table” and/or “Routing InformationBase,” or “RIB”) that it has obtained, with the generated subset(referred to as a “forwarding table” and/or “Forwarding InformationBase,” or “FIB”) including only the preferred routes (e.g., one routefor each IP address prefix), as determined based on the routing protocolin use and available information. Each router's generated FIB is used torapidly make forwarding decisions for network communication packets thatare received. In addition, in some situations, a router may generate andstore multiple alternative routes for a destination as part of its FIBinformation, such as to represent ECMP (“Equal Cost Multi-Path”) routinginformation that is received—if so, the router may use varioustechniques to select a particular one of the routes when forwarding anetwork packet to that destination. Thus, each router will typicallymake its own decisions regarding how to route network communicationpackets in an attempt to maximize the local operation of the networknear the router, using whatever information is locally available to therouter.

In at least some situations in which an embodiment of a configurablenetwork service provides a managed computer network as a virtualcomputer network overlaid on a substrate network, such routinginformation for the virtual computer network is not needed by theconfigurable network service to determine how to send networkcommunications to their final destinations. For example, if theconfigurable network service tracks the location in the substratenetwork of each computing node that is part of the virtual computernetwork, then network communications may in some situations be forwardedto a destination computing node over the substrate network without usingrouting information for the virtual computer network (althoughoptionally modifying the network communications to make changes thatwould have been made by appropriate virtual networking devices of thevirtual computer network if they were physically provided and used toforward the network communications, as discussed in greater detailelsewhere). However, the network topology and other configuration forthe virtual computer network may influence how network communicationsare forwarded between computing nodes in at least some other situations.As a simple illustrative example, consider a virtual computer networkthat is configured into two logical subnets, with one of the virtualnetwork computing nodes acting as a firewall that has distinct networkinterfaces in each of the two logical subnets to facilitate handlinginter-subnet network communications by performing analysis of andpossibly interdiction of such network communications that pass throughit. In such a situation, if the sending and destination computing nodesfor a network communication are in separate logical subnets, theconfigurable network service does not merely forward the communicationover the substrate network directly to the destination computingnode—instead, the logical network topology for the virtual computernetwork dictates that the configurable network service forward thecommunication from the sending computing node over the substrate networkto the intermediate firewall device computing node for handling, withthe communication sent to the network interface of the firewall devicecomputing node that is connected to the sending computing node's logicalsubnet. If the firewall device computing node passes the communicationon (optionally with modifications), the configurable network servicethen further forwards the communication over the substrate network fromthe other network interface of the firewall device computing node in theother logical subnet to the ultimate destination computing node.

In at least some embodiments and situations, the routing informationthat is forwarded over a managed virtual computer network by computingnodes of the virtual computer network may be of use to the configurablenetwork service in various manners, including to update network topologyinformation for the virtual computer network. For example, as acontinuation of the prior example having a virtual computer network withtwo logical subnets, the client associated with the virtual computernetwork may have initially configured the network topology of thevirtual computer network to have the two logical subnets and to havethem separated by at least one specified virtual network router or othervirtual networking device, but not have initially configured anyintermediate firewall device between the logical subnets. As discussedin greater detail elsewhere, such initial configuration information maybe supplied by the client using an API of the configurable networkservice, or instead in other manners. In addition, as noted above, insuch a situation, communications that are initially forwarded betweencomputing nodes in separate logical subnets may be directly sent to thedestination computing node over the substrate network, without havingthe communications pass through any intermediate computing nodes of thevirtual computer network. However, after the virtual computer network isin use and one or more such network communications have been forwardedbetween computing nodes, the client may dynamically make changes to thevirtual computer network that affect the network topology of the virtualcomputer network. As one example, the client may executefirewall-related software on one of the computing nodes of the virtualcomputer network, and that new firewall computing node may begin to actas the firewall device in the prior example, so as to analyzecommunications that pass between computing nodes of the two logicalsubnets. In order to detect this network topology change and takeappropriate actions, the configurable network service may interceptrouting-related communications that are sent by the new firewall devicein accordance with whatever routing protocol is used for the virtualcomputer network, and use the routing information included in thoserouting-related communications to detect the location and operation ofthe new firewall device, such as based on the network interfaces of thenew firewall device in the two logical subnets. In this manner, theconfigurable network service will determine to route subsequent networkcommunications between the logical subnets via the firewall device,using the network interfaces of the firewall device, in the mannerpreviously discussed.

Various routing protocols are defined and in use, and in at least someembodiments, the configurable network service may support the use ofsome or all of the various protocols (e.g., with a first managed virtualcomputer network that is provided by the configurable network serviceusing a first routing protocol, with a distinct second managed virtualcomputer network that is provided by the configurable network serviceusing one or more distinct second routing protocols, etc., and with theconfigurable network service extracting and using routing informationsent using the various routing protocols for the various managed virtualcomputer networks). A non-exclusive list of predefined routing protocolsthat may be supported by embodiments of the configurable network serviceincludes the following: OSPF (Open Shortest Path First); IS-IS(Intermediate System to Intermediate System); BGP (Border GatewayProtocol); RIP (Routing Information Protocol); IGRP (Interior GatewayRouting Protocol); EIGRP (Enhanced Interior Gateway Routing Protocol);RSVP (Resource ReSerVation Protocol); GARP (gratuitous addressresolution protocol); etc. Moreover, by supporting multiple routingprotocols that are in use by a single managed virtual computer network,the configurable network service may in some embodiments enable moreconsistent and/or accurate routing information to be provided tocomputing nodes of the managed virtual computer network that participatein one or more of those routing protocols. For example, consider asituation in which the managed virtual computer network has a firstcomputing node that uses a first routing protocol (e.g., BGP), which isconnected to a second computing node that uses a distinct second routingprotocol (e.g., OSPF), and the second computing node is connected to oneor more other third computing nodes that also use the first routingprotocol. In this situation, routing information that the firstcomputing node receives using the first routing protocol would typicallybe converted to the second routing protocol for the second computingnode, and then later converted back to the first routing protocol forthe third computing node(s)—however, such conversions may result in therouting information that is provided to the third computing nodes usingthe first routing protocol being different from the routing informationthat was originally provided to the first computing node using the firstrouting protocol (e.g., with respect to cost information for particularrouting paths or other information related to connectivity). Instead,some embodiments of the configurable network service may instead managethe routing information that is provided to the third computing nodesusing the first routing protocol to ensure that it is the same as orotherwise consistent with the routing information received by the firstcomputing node. More generally, if a particular group of routinginformation is sent to various computing nodes of a managed virtualcomputer network using two or more routing protocols, some embodimentsof the configurable network service may manage that routing informationto assist in maintaining consistency between the various routingprotocols' routing information.

In addition, various types of computing nodes may send routinginformation to the virtual networking devices of managed virtualcomputer networks in various embodiments. Such computing nodes may beprovided by the configurable network service and part of the virtualcomputer networks for which they send routing information (e.g., undercontrol of the client for whom the virtual computer network is beingprovided), or may include other types of computing nodes that are notpart of the virtual computer networks. For example, if a client operatesa separate computer network that interacts with a managed virtualcomputer network provided by an embodiment of the configurable networkservice (e.g., a remote computer network for which the managed virtualcomputer network is an extension), such as may interact via one or moreVPN connections or other connections, one or more computing nodes of theother computer network may in some embodiments and situations sendrouting-related communications that include such routing information ofpotential use to the configurable network service. In addition, thetypes of computing nodes that send such routing-related communicationsmay be actual network routers or other actual networking devices (e.g.,provided by and under control of the configurable network service and/orprovided by and under control of a client for whom a managed virtualcomputer network is being provided), and/or various other types ofcomputing nodes that may be configured (e.g., via software) to provideat least some types of functionality related to handling networkcommunications (e.g., firewalls; proxy devices; load balancers; VPNendpoints; intrusion detection and/or prevention systems; etc.), such ascomputing nodes of a managed virtual computer network provided for aclient that are configured by the client to operate as virtualappliances for the virtual computer network.

In addition, in order to facilitate handling of routing-relatedcommunications from other computing nodes to virtual networking devicesof managed virtual computer networks, embodiments of the configurablenetwork service may further take various actions to represent thevirtual networking devices to the other computing nodes. In particular,the configurable network service may in some embodiments assign at leastone network address for a virtual computer network to each virtualnetworking device for the virtual computer network, so as to enablerouting-related communications to be directed to the virtual networkingdevices using those assigned virtual network addresses. For example, ifa client specifies configuration information that indicates multiplevirtual network addresses to be used with a managed virtual computernetwork, each of the multiple computing nodes of the managed virtualcomputer network may be assigned at least one of those multiple virtualnetwork addresses, and each of the virtual networking devices may beassigned at least one other of those virtual network addresses that isdistinct from the virtual network addresses used for the multiplecomputing nodes (and for the other virtual networking devices). Asdiscussed in greater detail elsewhere, when network communications arereceived by the configurable network service that are directed to avirtual network address assigned to a virtual networking device, theconfigurable network service may intercept the communications, extractthe routing information from the communications, and use the extractedrouting information in various manners. In addition, in at least someembodiments, the configurable network service may further take actionsto send routing information to other computing nodes of a managedvirtual computer network (e.g., to send routing-related communicationsthat are spoofed to be or otherwise identified as being from virtualnetworking devices of the managed virtual computer network), such as inaccordance with the routing protocol(s) used for that managed virtualcomputer network. Such routing information may be sent to computingnodes of the managed virtual computer network, for example, for one ormore of the following reasons: to forward routing information directedto the virtual networking devices from other computing nodes; to provideupdates about routing-related changes that a client has made to themanaged virtual computer network by modifying configuration informationfor the virtual computer network, such as modifying network topologyinformation via an API of the configurable network service; etc. Thus,in at least some embodiments and situations, clients to whom managedvirtual computer networks are provided may be unaware that the virtualnetworking devices of their managed virtual computer networks are notphysically provided devices with which the other computing nodes areactually interacting, based on the actions of the configurable networkservice to emulate various functionality of those virtual networkingdevices, including corresponding to routing-related communications.

As previously noted, routing-related communications that are directed tovirtual networking devices of managed virtual computer networks may beintercepted and used by the configurable network service in varioussituations. For example, in at least some embodiments, each computingnode of a managed virtual computer network has an associatedcommunication manager module of the configurable network service thatmanages communications for the computing node. In such embodiments,those communication manager modules may perform at least some of thedescribed techniques. For example, when such a communication managermodule receives a routing-related communication from one of thecomputing nodes that it manages that is directed to a virtual networkingdevice, the communication manager module may identify that intendeddestination as being a virtual networking device (e.g., based on thedestination virtual network address used, based on a particular routingprotocol used for the communication, etc.), and instead process therouting-related communication so as to enable the routing information inthe communication to be used by the configurable network service. Insome embodiments, the communication manager module may extract therouting information from the routing-related communication, and forwardthe extracted routing information to another module of the configurablenetwork service for further processing (e.g., to a Network RoutingManager, or NRM, module). Furthermore, if a response message wouldtypically be provided by the intended destination virtual networkingdevice based on the routing protocol in use, the local communicationmanager module may generate and provide a spoofed response to the senderas appropriate that is indicated to be from the virtual networkingdevice. In other embodiments, the various communication manager modulesmay instead forward the routing-related communications to the NRM module(or other module) for similar processing by the NRM module, such as toenable the NRM module to extract the routing information. As previouslynoted, in at least some embodiments, the communication manager modulesand/or the NRM module may support multiple distinct routing protocols.

When the NRM module receives routing information from a routing-relatedcommunication directed to a virtual networking device of a managedvirtual computer network (whether directly from a communication managermodule, or after extracting the routing information from arouting-related communication received from the communication managermodule), the NRM module analyzes the routing information to determine ifit indicates any changes with respect to the previously known networktopology and connectivity information for the managed virtual computernetwork, such as that would affect how network communications are routedfor the managed virtual computer network (e.g., whether there areintermediate computing nodes of the managed virtual computer networkthrough which particular network communications are to be routed). Ifnetwork topology changes are identified for the managed virtual computernetwork, the NRM module takes actions to correspondingly update therouting information that is used for the managed virtual computernetwork. In particular, in at least some embodiments, the communicationmanager modules associated with computing nodes of managed virtualcomputer networks perform various actions to manage outgoing networkcommunications from their associated computing nodes, such as byforwarding those outgoing network communications to appropriatedestinations—in such embodiments, the communication manager module(s)that are associated with computing nodes of the managed virtual computernetwork that are affected by the identified network topology change maybe updated to handle network communications for those associatedcomputing nodes in a manner consistent with the identified networktopology change. For example, in the previously discussed situation inwhich a firewall device computing node of a managed virtual computernetwork is dynamically added between two logical subnets of that managedvirtual computer network, the communication manager module(s) associatedwith the computing nodes of those two logical subnets are updated tohandle new network communications between the two logical subnets in acorresponding manner. Thus, for a particular computing node in a firstof the two logical subnets, the associated communication manager moduleis updated so that destination virtual network addresses for othercomputing nodes of the first logical subnet will continue to be mappedto the substrate network locations of those other computing nodes (sothat communications directed to those computing nodes will be forwardeddirectly to those computing nodes over the substrate network), whiledestination virtual network addresses for computing nodes of the othersecond logical subnet will newly be mapped to the substrate networklocation of the firewall device computing node for further handling (sothat communications directed to those computing nodes will be forwardedover the substrate network to the firewall device for intermediatehandling).

Thus, the NRM module may obtain routing information from routing-relatedcommunications directed to virtual networking devices of a managedvirtual computer network, and use the routing information to update aconfigured network topology of the managed virtual computer network. Inaddition, in at least some embodiments, the NRM module may take furtheractions to facilitate the routing of network communications for such amanaged virtual computer network over an underlying substrate network inan appropriate manner. For example, when the managed virtual computernetwork is first created, the NRM module may use any configured networktopology information for the managed virtual computer network (e.g., asspecified via an API of the configurable network service) in a similarmanner to determine whether and when any network communications betweencomputing nodes of the managed virtual computer network are to bedirected through one or more intermediate computing nodes of the managedvirtual computer network based on the configured network topologyinformation, and configure the communication manager modules for thecomputing nodes of the managed virtual computer network in acorresponding manner. Similarly, if configured network topologyinformation for the managed virtual computer network is updated afterthe managed virtual computer network is in use, such as viaconfiguration information explicitly supplied by the associated clientto the system manager module of the configurable network service (e.g.,via an API and/or GUI provided by the configurable network service), theNRM module may similarly identify any network topology changes thataffect the routing of network communications, and update the appropriatecommunication manager modules to handle those network topology changesin an appropriate manner.

Furthermore, in addition to managing the routing of networkcommunications via the substrate network, the NRM module may use theobtained routing information for a managed virtual computer network inother manners in at least some embodiments. For example, when the NRMmodule identifies a change in network topology for the managed virtualcomputer network (whether from obtained routing information or from newnetwork topology configuration information received from the client),the NRM module may in some embodiments generate routing-relatedcommunications that include corresponding routing information in orderto update other computing nodes of the managed virtual computer network.Thus, for each of one or more of the computing nodes of the managedvirtual computer network that participate in the defined routingprotocol for the managed virtual computer network and that performfunctionality that involves handling network communications, the NRMmodule may instruct a communication manager module that manages thatcomputing node to supply that computing node with the routinginformation corresponding to the network topology change, such as bysending a routing-related communication to that communication managermodule that is destined for that computing node. Such a communicationsupplied to such a computing node of the managed virtual computernetwork may, for example, have spoofed sender information so that thecommunication appears to come from a virtual networking device of themanaged virtual computer network, or may instead be sent in othermanners in other embodiments.

When providing routing information for a managed virtual computernetwork to computing nodes of the managed virtual computer network, aswell as when providing substrate network routing information toparticular communication manager modules that manage communications forcomputing nodes of the managed virtual computer network, the NRM modulemay determine the routing information in a manner that is contextualizedto the recipient, as different computing nodes and/or communicationmanager modules typically route network communications differentlydepending on their network location (e.g., their relative location inthe configured network topology of the managed virtual computernetwork). Nonetheless, by having a centralized location for the variousinformation about the network topology of a managed virtual computernetwork, including in some embodiments to have a combination ofclient-supplied configuration information and dynamically suppliedrouting information from the actual managed virtual computer network,the NRM module may in some embodiments use the aggregate information todetermine consistent routing information to be used by the variouscomputing nodes of the managed virtual computer network (e.g., todetermine network paths for particular computing nodes to use that areglobally optimized for the managed virtual computer network, includingin light of network traffic from paths used by other computing nodes ofthe managed virtual computer network that facilitate handlingcommunications for the managed virtual computer network). Thus, ratherthan having each such network router and other computing node of themanaged virtual computer network independently attempt to determine bestpaths in a localized manner, the NRM module in such embodiments maycoordinate the routing information used across the managed virtualcomputer network, such as to maximize or otherwise enhance any desiredcriteria regarding characteristics of the operation of the managedvirtual computer network (e.g., to balance network traffic passingbetween multiple particular computing nodes, to minimize or maximizenetwork traffic passing through a particular computing node relative toone or more other computing nodes, etc.).

Furthermore, in at least some embodiments, the configurable networkservice may perform various actions to accomplish other goals. Forexample, in order to limit undesirable behavior, the configurablenetwork service may in some embodiments limit the types of changes tonetwork topology information that some or all computing nodes of amanaged virtual computer network are allowed to make. As one example, insome embodiments, some types of network topology changes may be limitedto being made via configuration information supplied to the systemmanager module of the configurable network service by the client, ratherthan via routing information from computing nodes of the managed virtualcomputer network, or vice versa. Furthermore, the configurable networkservice may limit the rate and/or total quantity of routing-relatedcommunications that some or all computing nodes of a managed virtualcomputer network are allowed to make. Such limiting of routing-relatedcommunications and/or other filtering of network topology changes may beperformed in various manners, including by the communication managermodules associated with the computing nodes that attempt to send suchrouting-related communications or otherwise make such network topologychanges (e.g., by discarding routing-related communications ifappropriate), and/or by the NRM module (e.g., by not updating theconfigured network topology for a managed virtual computer network inaccordance with disallowed network topology changes and/orrouting-related communications, such as by not updating communicationmanager modules for the computing nodes of the managed virtual computernetwork to support such changes).

Thus, a configurable network service may take various actions to supporta configured logical network topology for a managed computer network,such as to include one or more virtual networking devices as part of amanaged virtual computer network. As one example, the CNS system may usemultiple communication manager modules to transparently managecommunications sent by and to the computing nodes of the virtualcomputer network in a manner that emulates functionality that would beprovided by one or more virtual networking devices if they werephysically implemented for the virtual computer network and wereconfigured to route or otherwise forward the communications inaccordance with the specified network topology. Furthermore, theconfigurable network service may use multiple communication managermodules to emulate responses to networking requests made by computingnodes in the manner of a local physical networking device, such as torespond to ping requests, SNMP (“Simple Network Management Protocol”)queries, etc. In this manner, the configurable network service mayprovide virtual networking functionality that corresponds to a specifiednetwork topology for a managed virtual computer network that is providedby the configurable network service, but without the computing nodes ofthe virtual computer network (or the associated client user or otherentity) being aware that the actual computer network is not configuredin the normal manner to support the network topology and to physicallyinclude the virtual networking devices. Furthermore, as described ingreater detail below, in at least some embodiments, multiple modules ofthe configurable network service may operate together in a distributedmanner to provide functionality corresponding to a particular virtualnetworking device, such that no single module or physical device issingly responsible for emulating a particular virtual networking device.

In addition, as previously noted, the providing of networkingfunctionality for a managed virtual computer network may includesupporting connections between multiple managed virtual computernetworks. FIG. 1C illustrates an abstracted logical view of virtualcomputer networks that may be provided by an embodiment of theconfigurable network service, such as at the data center 190 of FIG. 1B,although the particular hardware computing systems and devices of FIG.1B are not illustrated. Instead, the logical view of FIG. 1C illustratesthat various computing nodes may be used to provide at least threemanaged computer networks 175, such as for one or more clients (notshown), such as by implementing the three managed computer networks 175as virtual networks that are overlaid on the various hardware computingsystems and devices. For example, the illustrated managed computernetwork 175 a in this example corresponds to the previously describedvirtual computer network that includes virtual machine computing nodes107 a 1, 107 c 1 and 107 d 1, as well as other computing nodes 102 a and102 b in this example, with the managed computer network 175 a beingprovided for a first client (not shown) in this example. The examplemanaged computer network 175 a is also configured in this example toinclude multiple specified networking devices, which are implemented asvirtual networking devices 103 a and 103 b (e.g., virtual routerdevices) in this example. Managed computer networks 175 b and 175 c alsoeach include various computing nodes and specified networking devices,and are each provided for a client (e.g., for second and third clientsthat are distinct from the first client; for the first client as well,such as if the first client is an organization and the different virtualcomputer networks are provided to different departments or other groupswithin the organization; etc.).

In the example of FIG. 1C, the configurable network service has providedtwo virtual peering routers 180 a and 180 b that enable interconnectionsbetween the managed computer networks 175 a, 175 b and 175 c, and whichare connected to each other via one or more logical connections 182 inthis example, although in other embodiments the interconnections betweenthe various managed computer networks may instead be provided by asingle peering router or by a peering fabric that includes more than twointerconnected peering routers. In this example, the illustrated virtualpeering routers include a first virtual peering router 180 a thatincludes virtual interfaces 181 a and 181 b corresponding to the managedcomputer networks 175 a and 175 b, respectively, and a second virtualpeering router 180 b that includes virtual interface 181 c correspondingto the managed computer network 175 c. Thus, in this example, the firstclient for whom managed computer network 175 a is provided configuresthe managed computer network 175 a to include a logical connection 104 ato the virtual interface 181 a of the virtual peering router 180 a. Theconnection 104 a enables the managed computer network 175 a to logicallyinteract with the virtual peering router 180 a to provide routinginformation for managed computer network 175 a and/or to receive routinginformation for one or both of managed computer networks 175 b and 175c, such as based on logical communications passed between the virtualpeering router 180 a and the virtual networking device 103 b, and basedon peering configuration information specified by the first client forthe connection 104 a. Such specified peering configuration informationmay be used, for example, to control whether other managed computernetworks are allowed to send routing information to and/or receiverouting information from the managed computer network 175 a, and tocontrol whether other managed computer networks are allowed to sendcommunications to and/or receive communications from computing nodes ofthe managed computer network 175 a, such as by defining one or morepolicies related to such communications. In some situations, at leastsome routing information may be initiated by one or more of thecomputing nodes of the managed computer network 175 a that participatein the routing protocol in use for managed computer network 175 a, suchas a computing node that is configured to operate for the managedcomputer network 175 a in a manner that facilitates communicationsbetween other computing nodes (e.g., to provide firewall capabilities,VPN endpoint capabilities, etc.). As discussed in greater detailelsewhere, in at least some embodiments, the virtual peering routers 180a and/or 180 b are not physically implemented using any actual routerdevices, and the configurable network service instead provides thefunctionality of the virtual peering routers 180 a and/or 180 b usingone or more modules of the configurable network service (e.g., in adistributed manner), such as the NRM module 170 of FIG. 1B, the SystemManager module 110 of FIG. 1B, and/or one or more of the CommunicationManager modules 109 and 150 of FIG. 1B.

In a manner similar to that of managed computer network 175 a, theclients for whom the managed computer networks 175 b and 175 c areprovided also configure those managed computer networks to connect withthe virtual peering routers 180 a and 180 b via logical connections 104b and 104 c to interfaces 181 b and 181 c, respectively. In particular,the example managed computer network 175 b includes multiple computingnodes 102 d and one or more specified virtual networking devices 103 c,and the connection 104 b is established between at least one of thevirtual networking devices 103 c and the virtual interface 180 b of thevirtual peering router 180 a. Similarly, the example managed computernetwork 175 c includes multiple computing nodes 102 e and one or morespecified virtual networking devices 103 d, and the connection 104 c isestablished between at least one of the virtual networking devices 103 dand the virtual interface 180 c of the virtual peering router 180 b.Routing information may also be passed between the virtual peeringrouters 180 and the managed computer networks 175 b and 175 c in amanner similar to that previously described for managed computer network175 a. In addition, in at least some embodiments, one or both themanaged computer networks 175 b and 175 c may have specified peeringconfiguration information for the connections 104 b and 104 c,respectively, in order to control how routing communications and/orcomputing node communications to and/or for the managed computernetworks 175 b and 175 c are handled, such as in accordance withpolicies specified for those managed computer networks by the client(s)for whom those managed computer networks are provided.

Thus, the virtual peering routers 180 a and 180 b may be configured invarious manners to support various types of functionality, whether byone or more of the clients that supplies peering configurationinformation in order to manage the connections 104 to their managedcomputer network, and/or by the configurable network service. Forexample, in some embodiments, one of the clients may request thecreation of one or both of the virtual peering routers 180 a and 180 b,and provide peering configuration information for those virtual peeringrouters, such as to indicate which clients or managed computer networksare allowed to connect to the virtual peering router, the types ofconnections and/or communications that are allowed for some or allconnected managed computer networks, etc. As one illustrative example,the managed computer network 175 a may initiate the creation of thevirtual peering router 180 a, and configure the virtual peering router18 a 0 in such a manner that the managed computer network 175 a isenabled to send communications to other managed computer networks thatsubsequently logically connect to the virtual peering router 180 a (suchas managed computer network 175 b directly, and managed computer network175 c via virtual peering router 180 b), but such that those othermanaged computer networks are not enabled to send communications to thecomputing nodes of the managed computer network 175 a (or are enabled tosend only a specified type of communication, such as HTTP requests to aparticular network address of the managed computer network 175 a,response communications to communications initiated by the managedcomputer network 175 a, etc.). In such a situation, the other managedcomputer networks may or may not be enabled to communicate with eachother. In order to inhibit the ability of the managed computer networks175 b and 175 c to send communications to the computing nodes of themanaged computer network 175 a, the peering configuration informationfor virtual peering router 180 a may block some or all routingcommunications from the managed computer network 175 a from being passedto the managed computer networks 175 b and 175 c, such as to prevent thespecified networking devices of the managed computer networks 175 b and175 c from having routing information corresponding to the managedcomputer network 175 a (and/or to other external computer systems, notshown, that are accessible from the managed computer network 175 a).However, while the virtual peering router 180 a may further beconfigured by the specified peering configuration information to blocksome or all communications from the managed computer networks 175 b and175 c that are directed to the computing nodes of the managed computernetwork 175 a, the specified peering configuration information may allowrouting communications from the managed computer networks 175 b and 175c to be forwarded to the managed computer network 175 a, such as tofacilitate the sending of communications from the managed computernetwork 175 a to the computing nodes of the managed computer networks175 b and 175 c. As a further example, the client for managed computernetwork 175 b may specify peering configuration information for virtualpeering router 180 a that authorizes communications to computing nodesof managed computer network 175 b from managed computer network 175 a(e.g., based on managed computer network having created virtual peeringrouter 180 a), but not from any other connected managed computernetworks (e.g., from managed computer network 175 c). However, theclient for managed computer network 175 c may specify peeringconfiguration information for virtual peering router 180 b thatauthorizes communications to computing nodes of managed computer network175 c for any other managed computer network (or may not specify anypeering configuration information, and the default peering configurationinformation for virtual peering router 180 b may enable suchcommunications from other managed computer networks), thus enabling bothmanaged computer networks 175 a and 175 b to send communications tocomputing nodes of managed computer network 175 c, but only managedcomputer network 175 a to send communications to computing nodes ofmanaged computer network 175 b. As an alternative example to thatdiscussed above, the virtual peering routers 180 a and 180 b may insteadbe configured to enable all connected managed computer networks to sendone or more types of communications to any other connected managedcomputer network. It will be appreciated that various other, morespecific configurations of the virtual peering routers 180 a and 180 bare possible.

As noted above, the virtual peering routers 180 a and 180 b may beconfigured to enable various types of communications to be exchangedbetween connected managed computer networks. In some embodiments, eachmanaged computer network that connects to the virtual peering routers180 a and 180 b may be allowed to specify peering configurationinformation that includes restrictions on the types of communicationsthat the managed computer network is willing to accept, such as toinclude one or more of the following: to specify a routing filter, suchas based on network address prefixes; to specify types of allowed ordisallowed communications, such as based on communication protocol,port, etc.; to specify particular other clients or managed computernetworks from which communications are allowed or disallowed; etc.). Insome embodiments, such a managed computer network may similarly be ableto specify restrictions on the types of communications that are allowedto be sent out from the managed computer network via the virtual peeringrouter, whether in addition to or instead of restrictions on incomingcommunications to the connected managed computer network from otherconnected managed computer networks. Furthermore, while not illustratedhere, particular connected managed computer networks may further haveconfigurations internal to those managed computer networks to assist inmanaging incoming and/or outgoing communications, such as one or morefirewall devices, intrusion detection systems, etc. Additional detailsrelated to configuration of virtual peering routers are included below.

Thus, as discussed with respect to FIG. 1C and elsewhere, the providingof networking functionality by a configurable network service mayinclude supporting connections between multiple managed virtual computernetworks, such as by providing one or more virtual peering routers towhich the managed virtual computer networks connect. Various otheraspects of providing managed computer networks are also described above,as well as elsewhere in this document, including to support virtualcomputer networks that are overlaid on an underlying substrate network.

Additional details are included below with respect to actions ofconfigurable network service embodiments to support networking devicesspecified for managed computer networks, such as for virtual networkingdevices that are not physically provided and whose functionality isemulated, as well as for obtaining and using routing information for amanaged computer network in various manners.

FIGS. 2A-2F illustrate further examples with additional illustrativedetails related to managing communications between computing nodes thatoccur via a virtual computer network overlaid over one or more physicalsubstrate networks, such as may be used by the computing nodes andnetworks of FIGS. 1A-1C, or in other situations. In these examples,FIGS. 2A and 2B illustrate details regarding actions of various modulesof an example CNS system in managing communications between computingnodes of a managed computer network, while FIGS. 2C and 2D illustrateadditional details regarding similar actions in managing communicationsin a manner specific to a particular specified network topology, such asthat includes virtual networking devices and/or intermediate computingnodes of the virtual computer network through which at least someinter-node communications pass. FIG. 2E illustrates additional detailsregarding obtaining and using routing information for a managed virtualcomputer network from routing-related communications directed to avirtual networking device of the managed virtual computer network, andFIG. 2F illustrates additional details regarding supportinginter-connections between multiple managed virtual computer networks.

In particular, FIG. 2A illustrates various example computing nodes 205and 255 that may communicate with each other by using one or moreintermediate inter-connection networks 250 as a substrate network. Inthis example, the inter-connection network 250 is an IPv6 substratenetwork on which IPv4 virtual computer networks are overlaid, althoughin other embodiments the inter-connection network 250 and overlayvirtual computer networks may use the same networking protocol (e.g.,IPv4). In addition, in this example embodiment, the computing nodes areoperated on behalf of multiple distinct entities to whom managed virtualcomputer networks are provided, and a System Manager module 290 managesthe association of particular computing nodes with particular entitiesand managed virtual computer networks, and tracks various configurationinformation specified for the managed virtual computer networks. Theexample computing nodes of FIG. 2A include four computing nodes executedon behalf of an example entity Z and part of a corresponding managedvirtual computer network provided for entity Z, those being computingnodes 205 a, 205 c, 255 a and 255 b. In addition, other computing nodesare operated on behalf of other entities and belong to other providedvirtual computer networks, such as computing node 205 b and othercomputing nodes 255.

In this example, the computing nodes 205 are managed by and physicallyconnected to an associated Communication Manager module R 210, and thecomputing nodes 255 are managed by and physically connected to anassociated Communication Manager module S 260. The CNS CommunicationManager modules 210 and 260 are physically connected to aninter-connection network 250, as is the System Manager module 290,although the physical inter-connections between computing nodes, modulesand the inter-connection network are not illustrated in this example. Asone example, computing nodes 205 may each be one of multiple virtualmachines hosted by a single physical computing system, and CommunicationManager module R may be part of a hypervisor virtual machine monitor forthat physical computing system. For example, with reference to FIG. 1B,computing nodes 205 may represent the virtual machines 107 a, andcomputing nodes 255 may represent the virtual machines 107 d. If so,Communication Manager module R would correspond to Communication Managermodule 109 a of FIG. 1B, Communication Manager module S would correspondto Communication Manager module 109 d of FIG. 1B, the inter-connectionnetwork 250 would correspond to inter-connection network 122 of FIG. 1B,and the System Manager module 290 would correspond to System Managermodule 110 of FIG. 1B. Alternatively, computing nodes 205 or 255 mayinstead each be a distinct physical computing system, such as tocorrespond to computing systems 155 a-155 n of FIG. 1, or to computingnodes at other data centers or geographical locations (e.g., computingsystems at another data center 160, computing systems 145 a, etc.).

Each of the Communication Manager modules of FIG. 2A is associated witha group of multiple physical substrate network addresses, which theCommunication Manager modules manage on behalf of their associatedcomputing nodes. For example, Communication Manager module R is shown tobe associated with the IPv6 network address range of “::0A:01/72”, whichcorresponds to the 128-bit addresses (in hexadecimal) from)XXXX:XXXX:XXXX:XXXA:0100:0000:0000:0000 to XXXX:XXXX:XXXX:XXXA:01FF:FFFF:FFFF:FFFF (representing 2 to the power of 56 unique IPv6addresses), where each “X” may represent any hexadecimal character thatis appropriate for a particular situation. The inter-connection network250 will forward any communication with a destination network address inthat range to Communication Manager module R—thus, with the initial 72bits of the range specified, the Communication Manager module R may usesubstrate network addresses that include the remaining available 56 bitsto represent the computing nodes that it manages and to determine how toprocess incoming communications whose destination network addresses arein that range.

For purposes of the example shown in FIG. 2A, computing nodes 205 a, 205c, 255 a, and 255 b are part of a single managed virtual computernetwork provided for entity Z, and have assigned IPv4 virtual networkaddresses for that virtual computer network of “10.0.0.2”, “10.0.5.1”,“10.0.0.3”, and “10.1.5.3”, respectively. Because computing node 205 bis part of a distinct managed virtual computer network that is providedfor entity Y, it can share the same virtual network address as computingnode 205 a without confusion. In this example, computing node A 205 aintends to communicate with computing node G 255 a, which are configuredin this example to be part of a single common physical sub-network (notshown) in a configured network topology for the managed virtual computernetwork, and the inter-connection network 250 and Communication Managermodules are transparent to computing nodes A and G in this example. Inparticular, despite the physical separation of computing nodes A and G,the Communication Manager modules 210 and 260 operate so as to overlaythe managed virtual computer network for entity Z over the physicalinter-connection network 250 for communications between those computingnodes, including to emulate functionality corresponding to theconfigured sub-network of the managed virtual computer network, so thatthe lack of an actual corresponding network is transparent to thecomputing nodes A and G.

In order to send the communication to computing node G, computing node Aexchanges various messages 220 with Communication Manager module R 210,despite in the illustrated embodiment being unaware of the existence ofCommunication Manager module R (i.e., computing node A may believe thatit is transmitting a broadcast message to all other nodes on the localsub-network, such as via a specified switching device that computingnode A believes connects the nodes on the local sub-network). Inparticular, in this example, computing node A first sends an ARP messagerequest 220-a that includes the virtual network address for computingnode G (i.e., “10.0.0.3”) and that requests the corresponding hardwareaddress for computing node G (e.g., a 48-bit MAC address). CommunicationManager module R intercepts the ARP request 220-a, and responds tocomputing node A with a spoofed ARP response message 220-b that includesa virtual hardware address for computing node G.

To obtain the virtual hardware address for computing node G to use withthe response message, the Communication Manager module R first checks alocal store 212 of information that maps virtual hardware addresses tocorresponding IPv6 actual physical substrate network addresses, witheach of the virtual hardware addresses also corresponding to an IPv4virtual network address for a particular entity's managed virtualcomputer network. If the local store 212 does not contain an entry forcomputing node G (e.g., if none of the computing nodes 205 havepreviously communicated with computing node G and the System Managermodule 290 does not push mapping information to the CommunicationManager Module R without request, if a prior entry in local store 212for computing node G has expired based on an associated expiration time,etc.), the Communication Manager module R interacts 225 with SystemManager module 290 to obtain the corresponding actual IPv6 physicalsubstrate network address for computing node G on behalf of computingnode A. In particular, in this example, the System Manager module 290maintains provisioning information 292 that identifies where eachcomputing node is actually located and to which entity and/or managedvirtual computer network the computing node belongs, such as byinitiating execution of programs on computing nodes for entities andvirtual computer networks or by otherwise obtaining such provisioninginformation. As discussed in greater detail with respect to FIG. 2B, theSystem Manager module may determine whether the request fromCommunication Manager module R on behalf of computing node A forcomputing node G's actual IPv6 physical substrate network address isvalid, including whether computing node A is authorized to communicatewith computing node G (e.g., such as based on being part of the sameconfigured local area sub-network), and if so provides that actual IPv6physical substrate network address. While the interactions 225 with theSystem Manager module 290 are not illustrated in this example asexplicitly traveling over the inter-connection network 250, it will beappreciated that such interactions may include one or morecommunications that do travel over the inter-connection network 250 inat least some embodiments.

Communication Manager module R receives the actual IPv6 physicalsubstrate network address for computing node G from the System Managermodule 290, and stores this received information as part of an entry forcomputing node G in mapping information 212 for later use (optionallywith an expiration time and/or other information). In addition, in thisexample, Communication Manager module R determines a virtual hardwareaddress to be used for computing node G (e.g., by generating a dummyidentifier that is locally unique for the computing nodes managed byCommunication Manager module R), stores that virtual hardware address inconjunction with the received actual IPv6 physical substrate networkaddress as part of the mapping information entry, and provides thevirtual hardware address to computing node A as part of response message220-b. By maintaining such mapping information 212, later communicationsfrom computing node A to computing node G may be authorized byCommunication Manager module R without further interactions with theSystem Manager module 290, based on the use of the virtual hardwareaddress previously provided by Communication Manager module R. In someembodiments, the hardware address used by Communication Manager module Rfor computing node G may not be a dummy address, such as if SystemManager module 290 further maintains information about hardwareaddresses used by the various computing nodes (e.g., virtual hardwareaddresses assigned to virtual machine computing nodes, actual hardwareaddresses assigned to physical computing systems acting as computingnodes, etc.) and provides the hardware address used by computing node Gto Communication Manager module R as part of the interactions 225. Insuch embodiments, the Communication Manager module R may take furtheractions if computing nodes on different virtual networks use the samevirtual hardware address, such as to map each combination of computingnode hardware address and managed virtual computer network to acorresponding substrate network address.

In other embodiments, Communication Manager module R may interact withSystem Manager module 290 to obtain a physical substrate network addressfor computing node G or otherwise determine such a physical substratenetwork address at times other than upon receiving an ARP request, suchas in response to any received communication that is directed tocomputing node G using the virtual network address “10.0.0.3” as part ofentity Z's virtual computer network, or if the System Manager moduleprovides that information to Communication Manager module R withoutrequest (e.g., periodically; upon changes in the information, such aschanges in network topology information for the managed virtual computernetwork; etc.). Furthermore, in other embodiments, the virtual hardwareaddresses that are used may differ from this example, such as if thevirtual hardware addresses are specified by the System Manager module290, if the virtual hardware addresses are not random and instead storeone or more types of information specific to the corresponding computingnodes, etc. In addition, in this example, if computing node A had notbeen determined to be authorized to send communications to computingnode G, whether by the System Manager module 290 and/or CommunicationManager module R, Communication Manager module R would not send theresponse message 220-b with the virtual hardware address (e.g., insteadsends no response or an error message response).

In this example, the returned IPv6 actual physical substrate networkaddress corresponding to computing node G in interactions 225 is“::0B:02:<Z-identifier>10.0.0.3”, where “10.0.0.3” is stored in the last32 bits of the 128-bit IPv6 address, and where “<Z-identifier>” is a24-bit entity network identifier for computing node G corresponding tothe managed virtual computer network for entity Z (e.g., as previouslyassigned by the System Manager module to that network to reflect arandom number or some other number corresponding to the entity). Theinitial 72 bits of the IPv6 network address store the “::0B:02”designation, corresponding to the sub-network or other portion of thephysical inter-connection network with a network address range of“::0B:02/72” to which Communication Manager module S corresponds—thus, acommunication sent over the inter-connection network 250 to IPv6destination network address “::0B:02:<Z-identifier>:10.0.0.3” will berouted to Communication Manager module S. In other embodiments, theentity network identifier may be other lengths (e.g., 32 bits, ifCommunication Manager module S has an associated network address rangeof 64 bits rather than 56 bits) and/or may have other forms (e.g., maybe random, may store various types of information, etc.), and theremaining 56 bits used for the network address range after the “::0B:02”designation may store other types of information (e.g., an identifierfor a particular entity, a tag or label for the virtual computernetwork, an identifier for a particular specified VLAN to whichcomputing node G is assigned, etc.). In other embodiments, some or allsuch information may instead be stored and/or transmitted with acommunication to computing node G in other manners, such as by includingthe information in a header of the communication, including insituations in which the substrate network uses the IPv4 networkingprotocol.

After receiving the response message 220-b from Communication Managermodule R, computing node A creates and initiates the sending of aninter-node communication to computing node G, shown in FIG. 2A ascommunication 220-c. In particular, the header of communication 220-cincludes a destination virtual network address for destination computingnode G that is “10.0.0.3”, a destination hardware address fordestination computing node G that is the virtual hardware addressprovided to computing node A in message 220-b, a source virtual networkaddress for sending computing node A that is “10.0.0.2”, and a sourcehardware address for sending computing node A that is an actual or dummyhardware address that was previously identified to computing node A(e.g., by Communication Manager module R, based on prior configurationof computing node A, etc.). Since computing node A believes thatcomputing node G is part of the same local sub-network as itself,computing node A does not need to direct the communication 220-c to anyintermediate virtual router devices that are configured in a networktopology for the managed virtual computer network to separate thecomputing nodes. Furthermore, in this example, there are no othercomputing nodes of the managed virtual computer network through whichthis inter-node communication is configured to pass.

Communication Manager module R intercepts the communication 220-c,modifies the communication as appropriate, and forwards the modifiedcommunication over the inter-connection network 250 to computing node G.In particular, Communication Manager module R extracts the virtualdestination network address and virtual destination hardware address forcomputing node G from the header, and then retrieves the IPv6 actualphysical substrate network address corresponding to that virtualdestination hardware address from mapping information 212. As previouslynoted, the IPv6 actual physical substrate network address in thisexample is “::0B:02:<Z-identifier>:10.0.0.3”, and Communication Managermodule R creates a new IPv6 header that includes that actual physicalsubstrate network address as the destination address. Similarly, theCommunication Manager module R extracts the virtual source networkaddress and virtual source hardware address for computing node A fromthe header of the received communication, obtains an IPv6 actualphysical substrate network address corresponding to that virtual sourcehardware address (e.g., from a stored entry in mapping information 212,by interacting with the System Manager module 290 to obtain thatinformation if not previously obtained, etc.), and includes that actualphysical substrate network address as the source network address for thenew IPv6 header. In this example, the IPv6 actual physical substratenetwork address for computing node A is“::0A:01:<Z-identifier>10.0.0.2”, which if used in a reply byCommunication Manager module S on behalf of computing node G will berouted to Communication Manager module R for forwarding to computingnode A. The Communication Manager module R then creates communication230-3 by modifying communication 220-c so as to replace the prior IPv4header with the new IPv6 header (e.g., in accordance with SIIT),including populating the new IPv6 header with other information asappropriate for the communication (e.g., payload length, traffic classpacket priority, etc.). Thus, the communication 230-3 includes the samecontent or payload as communication 220-c, without encapsulating thecommunication 220-c within the communication 230-3 in this example.Furthermore, access to the specific information within the payload isnot needed for such re-headering, such as to allow Communication Managermodule R to handle communications in which the payload is encryptedwithout needing to decrypt that payload.

In at least some embodiments, before forwarding communication 230-3 toCommunication Manager module S, Communication Manager module R mayperform one or more actions to determine that communication 220-c isauthorized to be forwarded to computing node G as communication 230-3,such as based on the mapping information 212 including a valid entry forthe destination virtual hardware address used in communication 220-c(e.g., an entry specific to sending computing node 205 a in someembodiments, or instead an entry corresponding to any of the computingnodes 205 in other embodiments). In other embodiments, such anauthorization determination may not be performed by CommunicationManager module R for each outgoing communication, or instead may beperformed in other manners (e.g., based on a determination that thesending node and destination node are part of the same managed virtualcomputer network, are associated with the same entity, or are otherwiseauthorized to inter-communicate; based on an interaction with SystemManager module 290 to obtain an authorization determination for thecommunication; etc.).

After Communication Manager module R forwards the modified communication230-3 to the inter-connection network 250, the inter-connection networkuses the physical IPv6 destination network address of the communicationto route the communication to Communication Manager module S. In doingso, the devices of the inter-connection network 250 do not use theportion of the destination network address that includes the embeddedentity network identifier or embedded virtual network address, and thusdo not need any special configuration to forward such a communication,nor even awareness that a managed virtual computer network is beingoverlaid on the physical inter-connection network.

When Communication Manager module S receives communication 230-3 via theinter-connection network 250, it performs actions similar to those ofCommunication Manager module R, but in reverse. In particular, in atleast some embodiments, the Communication Manager module S verifies thatcommunication 230-3 is legitimate and authorized to be forwarded tocomputing node G, such as via one or more interactions 240 with theSystem Manager module. As with the interactions 225, it will beappreciated that the interactions 240 may include one or morecommunications (not shown) that travel over the inter-connection network250 in at least some embodiments. If the communication 230-3 isdetermined to be authorized (or if the authorization determination isnot performed), the Communication Manager module S then modifiescommunication 230-3 as appropriate and forwards the modifiedcommunication to computing node G. Additional details related to theverification of the communication 230-3 are discussed with respect toFIG. 2B.

In particular, to modify communication 230-3, Communication Managermodule S retrieves information from mapping information 262 thatcorresponds to computing node G, including the virtual hardware addressused by computing node G (or generates such a virtual hardware addressif not previously available, such as for a new computing node).Communication Manager module S then creates communication 245-e bymodifying communication 230-3 so as to replace the prior IPv6 headerwith a new IPv4 header (e.g., in accordance with SIIT). The new IPv4header includes the virtual network address and virtual hardware addressfor computing node G as the destination network address and destinationhardware address for the new IPv4 header, the virtual network addressand a virtual hardware address for computing node A as the sourcenetwork address and source hardware address for the new IPv4 header, andincludes other information as appropriate for the communication (e.g.,total length, header checksum, etc.). The virtual hardware address usedby Communication Manager module S for computing node A may be the sameas the hardware address used by Communication Manager module R forcomputing node A, but in other embodiments each Communication Managermodule may maintain separate hardware address information that is notrelated to the information used by the other Communication Managermodules (e.g., if Communication Manager module S generated its own dummyvirtual hardware address for computing node A in response to a prior ARPrequest from one of the computing nodes 255 for computing node A'shardware address). Thus, the communication 245-e includes the samecontent or payload as communications 220-c and 230-3. CommunicationManager module S then forwards communication 245-e to computing node G.

After receiving communication 245-e, computing node G determines to senda response communication 245-f to computing node A, using the sourcevirtual network address and source virtual hardware address forcomputing node A from communication 245-e. Communication Manager moduleS receives response communication 245-f, and processes it in a mannersimilar to that previously described with respect to communication 220-cand Communication Manager module R. In particular, Communication Managermodule S optionally verifies that computing node G is authorized to sendcommunications to computing node A (e.g., based on being a response to aprevious communication, or otherwise based on configuration informationfor computing nodes A and G as previously described), and then modifiescommunication 245-f to create communication 230-6 by generating a newIPv6 header using mapping information 262. After forwardingcommunication 230-6 to the inter-connection network 250, thecommunication is sent to Communication Manager module R, which processesthe incoming communication in a manner similar to that previouslydescribed with respect to communication 230-3 and Communication Managermodule S. In particular, Communication Manager module R optionallyverifies that computing node G is authorized to send communications tocomputing node A and that communication 230-6 actually was sent from thesubstrate network location of computing node G, and then modifiescommunication 230-6 to create response communication 220-d by generatinga new IPv4 header using mapping information 212. Communication Managermodule R then forwards response communication 220-d to computing node A.In some embodiments and situations, Communication Manager modules Rand/or S may handle response communications differently from initialcommunications, such as to assume that response communications areauthorized in at least some situations, and to not perform some or allauthorization activities for response communications in thosesituations.

In this manner, computing nodes A and G may inter-communicate using aIPv4-based managed virtual computer network, without any specialconfiguration of those computing nodes to handle the actual interveningIPv6-based substrate inter-connection network, and inter-connectionnetwork 250 may forward IPv6 communications without any specialconfiguration of any physical networking devices of the inter-connectionnetwork, based on the Communication Manager modules overlaying thevirtual computer network over the actual physical inter-connectionnetwork from the edges of the inter-connection network.

In addition, while not illustrated with respect to FIG. 2A, in at leastsome embodiments the Communication Manager modules may receive andhandle other types of requests and communications on behalf ofassociated computing nodes. For example, Communication Manager modulesmay take various actions to support broadcast and multicast capabilitiesfor computing nodes that they manage. As one example, in someembodiments, a special multicast group virtual network address suffixmay be reserved from each entity network identifier prefix for use insignaling networking Layer 2 raw encapsulated communications. Similarly,for link-local broadcast and multicast communications, a specialmulticast group /64 prefix may be reserved (e.g., “FF36:0000::”), whilea different destination address prefix (e.g., “FF15:0000::”) may be usedfor other multicast communications. Thus, for example, multicast andbroadcast IP frames may be encapsulated using a corresponding reserved64-bit prefix for the first 64 bits of the 128-bit IPv6 address, withthe remaining 64 bits including the virtual IPv4 network address for thedestination computing node and the entity network identifier for thedestination computing node in a manner similar to that previouslydescribed. Alternatively, in other embodiments, one or more types ofbroadcast and/or multicast communications may each have a correspondingreserved label or other identifier that has a different value or form,including using a different number of bits and/or being stored in amanner other than as a network address prefix. When a computing nodesends a broadcast/multicast communication, any Communication Managermodule with an associated computing node that has subscribed to thatmulticast/broadcast group would be identified (e.g., based on thoseCommunication Manager modules having subscribed to the group, such as inresponse to prior join communications sent by those associated computingnodes), and the Communication Manager module for the sending computingnode would forward the communication to each of the identifiedCommunication Manager modules of the group, for forwarding to theirappropriate managed computing nodes. In addition, in some embodimentsand situations, at least some broadcast or multicast communications maynot be forwarded by Communication Manager modules, such ascommunications with an IPv4 prefix of 224.0/16 or another designatedprefix or other label or identifier.

In addition to supporting broadcast and multicast capabilities formanaged computing nodes, the Communication Manager modules may receiveand handle other types of requests and communications on behalf ofassociated computing nodes that correspond to configured networktopologies for the virtual computer networks to which the computingnodes belong. For example, computing nodes may send various requeststhat a specified local router device or other specified networkingdevice would be expected to handle (e.g., ping requests, SNMP queries,etc.), and the associated Communication Manager modules may interceptsuch requests and take various corresponding actions to emulate thefunctionality that would have been provided by the specified networkingdevice if it was physically implemented. Furthermore, in at least someembodiments, Communication Manager modules may receive and handlerouting-related communications that are directed to virtual networkingdevices rather than to computing nodes of the managed virtual computernetwork, as discussed in greater detail with respect to FIG. 2E.

In addition, it will be appreciated that a Communication Manager modulemay facilitate communications between multiple of the computing nodesthat are associated with that Communication Manager module. For example,with respect to FIG. 2A, computing node 205 a may wish to send anadditional communication (not shown) to computing node 205 c. If so,Communication Manager module R would perform actions similar to thosepreviously described with respect to the handling of outgoingcommunication 220-c by Communication Manager module R and the handlingof incoming communication 230-3 by Communication Manager module S, butwithout re-headering of the additional communication to use an IPv6header (since the communication will not travel over theinter-connection network). However, if computing nodes 205 a and 205 care configured in a network topology for the virtual computer network tobe separated by one or more virtual networking devices, theCommunication Manager module R may take additional actions to emulatethe functionality of those virtual networking devices, as discussed ingreater detail with respect to FIG. 2C. Similarly, if computing nodes205 a and 205 c are configured in a network topology for the virtualcomputer network to be separated by one or more other intermediatecomputing nodes of the virtual computer network through which suchcommunications are to pass, the Communication Manager module R may takeadditional actions to forward such communications to such intermediatecomputing nodes, as discussed in greater detail with respect to FIG. 2D.

While not illustrated with respect to FIG. 2A, in at least someembodiments other types of requests and communications may also behandled in various ways. For example, in at least some embodiments, anentity may have one or more computing nodes that are managed byCommunication Manager module(s) and that are part of a managed virtualcomputer network for that entity, and may further have one or more othernon-managed computing systems (e.g., computing systems that are directlyconnected to the inter-connection network 250 and/or that natively useIPv6 network addressing) that do not have an associated CommunicationManager module that manages their communications. If the entity desiresthat those non-managed computing systems be part of that virtualcomputer network or otherwise communicate with the managed computingnodes of the virtual computer network, such communications betweenmanaged computing nodes and non-managed computing systems may be handledby the Communication Manager module(s) that manage the one or morecomputing nodes in at least some such embodiments. For example, in suchsituations, if such a non-managed computing system is provided with anactual IPv6 destination network address for such a managed computingnode (e.g., “::0A:01:<Z-identifier>:10.0.0.2” for managed computing nodeA in this example), the non-managed computing system may sendcommunications to computing node A via inter-connection network 250using that destination network address, and Communication Manager moduleR would forward those communications to computing node A (e.g., afterre-headering the communications in a manner similar to that previouslydescribed) if Communication Manager module R is configured to acceptcommunications from that non-managed computing system (or from anynon-managed computing system). Furthermore, Communication Manager moduleR may generate a dummy virtual network address to correspond to such anon-managed computing system, map it to the actual IPv6 network addressfor the non-managed computing system, and provide the dummy virtualnetwork address to computing node A (e.g., as the source network addressfor the communications forwarded to computing node A from thenon-managed computing system), thus allowing computing node A to sendcommunications to the non-managed computing system.

Similarly, in at least some embodiments and situations, at least somemanaged computing nodes and/or their virtual computer networks may beconfigured to allow communications with other devices that are not partof the virtual computer network, such as other non-managed computingsystems or other types of network appliance devices that do not have anassociated Communication Manager module that manages theircommunications. In such situations, if the managed computing nodesand/or the virtual computer network is configured to allowcommunications with such other non-managed devices, such a non-manageddevice may similarly be provided with the actual IPv6 destinationnetwork address for such a computing node (e.g.,“::0A:01:<Z-identifier>:10.0.0.2” for computing node A in this example),allowing the non-managed device to send communications to computing nodeA via inter-connection network 250 using that destination networkaddress, with Communication Manager module R then forwarding thosecommunications to computing node A (e.g., after re-headering thecommunications in a manner similar to that previously described).Furthermore, Communication Manager module R may similarly manageoutgoing communications from computing node A to such a non-manageddevice to allow computing node A to send such communications.

In addition, as previously noted, a communication manager module managescommunications for associated computing nodes in various ways, includingin some embodiments by assigning virtual network addresses to computingnodes of a provided virtual computer network, and/or by assigningsubstrate physical network addresses to managed computing nodes from arange of substrate physical network addresses that correspond to thecommunication manager module. In other embodiments, some such activitiesmay instead be performed by one or more computing nodes of the virtualcomputer network, such as to allow a DHCP (Dynamic Host ConfigurationProtocol) server or other device of a virtual computer network tospecify virtual network addresses and/or substrate physical networkaddresses for particular computing nodes of the virtual network. In suchembodiments, the communication manager module obtains such configurationinformation from the virtual network device(s), and updates its mappinginformation accordingly (and in some embodiments may further update oneor more system manager modules that maintain information about computingnodes associated with virtual networks). In yet other embodiments, auser or other entity associated with a virtual computer network maydirectly configure particular computing nodes to use particular virtualnetwork addresses. If so, the communication manager modules and/orsystem manager module may track which virtual network addresses are usedby particular computing nodes, and similarly update stored mappinginformation accordingly.

In addition, in some embodiments and situations, a managed computingnode may itself be treated as a phantom router, with multiple virtualnetwork addresses associated with that managed computing node, and withthat managed computing node forwarding communications to other computingnodes that correspond to those multiple virtual network addresses. Insuch embodiments, the communication manager module that managescommunications for that managed router computing node handlescommunications to and from that computing node in a manner similar tothat previously described. However, the communication manager module isconfigured with the multiple virtual network addresses that correspondto the managed router computing node, so that incoming communications toany of those multiple virtual network addresses are forwarded to themanaged router computing node, and so that outgoing communications fromthe managed router computing node are given a substrate source physicalnetwork address that corresponds to the particular computing node thatsent the communication via the managed router computing node. In thismanner, routers or other networking devices of a particular customer orother entity may be virtually represented for a virtual computer networkimplemented for that entity.

FIG. 2B illustrates some of the computing nodes and communicationsdiscussed with respect to FIG. 2A, but provides additional details withrespect to some actions taken by the Communication Manager modules 210and 260 and/or the System Manager module 290 to authorize communicationsbetween computing nodes. For example, after computing node A sendsmessage 220-a to request a hardware address for computing node G,Communication Manager module R may perform one or more interactions 225with the System Manager module 290 in order to determine whether toprovide that information, such as based on whether computing node A isauthorized to communicate with computing node G, as well as to determinea corresponding substrate physical network address for computing node Gbased on inter-connection network 250. If the Communication Managermodule R has previously obtained and stored that information and itremains valid (e.g., has not expired), then the interactions 225 may notbe performed. In this example, to obtain the desired physical networkaddress corresponding to computing node G, Communication Manager moduleR sends a message 225-1 to the System Manager module 290 that includesthe virtual network addresses for computing nodes A and G, and thatincludes an entity network identifier for each of the computing nodes,which in this example is an entity network identifier for the managedvirtual computer network of entity Z (e.g., a 32-bit or 24-bit uniqueidentifier). In at least some embodiments, Communication Manager moduleR may send message 225-1 to the System Manager module 290 using ananycast addressing and routing scheme, so that multiple System Managermodules (not shown) may be implemented (e.g., one for each data centerthat includes Communication Manager modules and associated computingnodes) and an appropriate one of those (e.g., the nearest, the mostunderutilized, etc.) is selected to receive and handle the message.

After the System Manager module 290 determines that computing node A isauthorized to communicate with computing node G (e.g., based on havingthe same entity network identifier, based on computing node A having anentity network identifier that is authorized to communicate withcomputing nodes of the entity network identifier for computing node G,based on other information provided by or associated with computing nodeA indicating that computing node A is authorized to perform suchcommunications, based on information provided by or associated withcomputing node G indicating that computing node A is authorized toperform such communications, based on the configured network topologyfor the managed virtual computer network to which computing nodes A andG belong, etc.), the System Manager module 290 returns a responsemessage 225-2 that includes the desired actual physical substratenetwork address corresponding to computing node G. In addition, in atleast some embodiments, before sending the desired actual physicalnetwork address, the System Manager module 290 may further verify thatCommunication Manager module R is authorized to send the message 225-1on behalf of computing node A, such as based on computing node A beingdetermined to be one of the computing nodes with which CommunicationManager module R is associated.

In other embodiments, Communication Manager module R may perform some orall of the actions described as being performed by System Manager module290, such as to maintain provisioning information for the variouscomputing nodes and/or to determine whether computing node A isauthorized to send communications to computing node G, or instead nosuch authorization determination may be performed in some or allsituations. Furthermore, in other embodiments, other types ofauthorization determinations may be performed for a communicationbetween two or more computing nodes, such as based on a type of thecommunication, on a size of the communication, on a time of thecommunication, etc.

As previously noted with respect to FIG. 2A, after Communication Managermodule S receives communication 230-3 intended for computing node G viathe inter-connection network 250, Communication Manager module S mayperform one or more interactions 240 with the System Manager module 290in order to determine whether to authorize that communication. Inparticular, in this example, to verify that the communication 230-3 isvalid and authorized to be forwarded to computing node G, CommunicationManager module S first extracts the actual IPv6 destination networkaddress and actual IPv6 source network address from the header ofcommunication 230-3, and then retrieves the embedded entity networkidentifiers and virtual network addresses from each of the extractedIPv6 network addresses. The Communication Manager module S nextexchanges messages 240 with System Manager module 290 to obtain thecorresponding actual IPv6 physical network address for the sendingcomputing node A on behalf of computing node G, including a message240-4 that includes the extracted virtual network addresses forcomputing nodes A and G and the entity network identifier for each ofthe computing nodes. In at least some embodiments, Communication Managermodule S may send message 240-4 to the System Manager module 290 usingan anycast addressing and routing scheme, as previously described.

The System Manager module 290 receives message 240-4, and returns aresponse message 240-5 that includes the actual physical substratenetwork address corresponding to computing node A, which in this exampleis “::0A:01:<Z-identifier>:10.0.0.2”. As previously discussed withrespect to messages 225-1 and 225-2, in some embodiments the SystemManager module 290 and/or Communication Manager module S may furtherperform one or more other types of authorization determinationactivities, such as to determine that computing node G is authorized tocommunicate with computing node A, that Communication Manager module Sis authorized to send the message 240-4 on behalf of computing node G,etc. Communication Manager module S then verifies that the returnedphysical network address in response message 240-5 matches the sourceIPv6 network address extracted from the header of communication 230-3,so as to prevent attempts to spoof messages as being from computing nodeA that are actually sent from other computing nodes in other locations.Communication Manager module S optionally stores this receivedinformation from response message 240-5 as part of an entry forcomputing node A in mapping information 262 for later use, along withcomputing node A's virtual network address and a virtual hardwareaddress for computing node A.

FIG. 2C illustrates a further example of managing ongoing communicationsfor the virtual computer network described with respect to FIGS. 2A and2B, but with communications being managed to support virtual networkingfunctionality for the virtual computer network in accordance with aconfigured network topology for the virtual computer network. Thenetwork topology information may be configured for the managed virtualcomputer network in various manners and at various times. For example,entity Z 285 may directly interact with the System Manager module 290 toprovide the configured network topology information, such as via an API(not shown) and/or GUI (not shown) that is provided by the module 290 tofacilitate obtaining such configuration information. In addition, thenetwork topology information may be configured, for example, as part ofinitially creating the virtual computer network for entity Z, and insome embodiments may further be dynamically updated while the virtualcomputer network is in use.

The example of FIG. 2C illustrates computing node A, CommunicationManager modules R and S, System Manager module 290, and inter-connectionnetwork 250 in a manner similar to that shown in FIGS. 2A and 2B.However, FIG. 2C further illustrates additional information regardingcomputing node A 205 a and computing node H 255 b as compared to FIG.2A, as well as logical representations 270 a and 270 b of two specifiedrouter devices that are part of the configured network topology for themanaged virtual computer network but that are not actually physicallyimplemented as part of providing the managed virtual computer network.In particular, in this example, computing node A is sending acommunication to computing node H, and the actions of the physicallyimplemented modules 210 and 260 and devices of network 250 in actuallysending the communication are shown, as well as emulated actions of thevirtual router devices 270 a and 270 b in logically sending thecommunication.

In this example, computing nodes A and H are configured to be part oftwo distinct sub-networks of the virtual computer network, and thevirtual router devices 270 a and 270 b separate the computing nodes Aand H in the configured network topology for the virtual computernetwork. For example, virtual router device J 270 a may be a localrouter device to computing node A in the configured network topology(e.g., may manage a first sub-network that includes computing node A),and virtual router device L 270 b may be a local router device tocomputing node H in the configured network topology (e.g., may manage adistinct second sub-network that includes computing node H). Whilecomputing nodes A and H are illustrated as being separated by two routerdevices in the configured network topology in this example, it will beappreciated that two such computing nodes may be separated by 0, 1 ormore than 2 router devices in other situations, and that other types ofnetworking devices may separate computing nodes in some situations.

In the example of FIG. 2C, the additional information that is shown forcomputing nodes A and H includes hardware addresses associated withthose computing nodes for the virtual computer network, such as virtualhardware addresses that are assigned to the computing nodes by theSystem Manager module 290 and/or the Communication Manager modules R andS. In particular, in this example, computing node A has been assignedhardware address “00-05-02-0B-27-44,” and computing node H has beenassigned hardware address “00-00-7D-A2-34-11.” In addition, the virtualrouter devices J and L have also each been assigned virtual hardwareaddresses, which in this example are “00-01-42-09-88-73” and“00-01-42-CD-11-01,” respectively, and have been assigned virtualnetwork addresses, which in this example are “10.0.0.1” and “10.1.5.1,”respectively. The various hardware addresses will be used as part of thesending of the communication from computing node A to computing node H,and the providing of corresponding virtual networking functionality forthe virtual computer network, as described below.

Thus, in a manner similar to that described with respect to FIG. 2A,computing node A determines to send a communication to computing node H,and accordingly exchanges various messages 222 with CommunicationManager module R 210. In particular, in this example, computing node Afirst sends an ARP message request 222-a for virtual hardware addressinformation. However, unlike the example of FIG. 2A in which computingnodes A and G were part of the same logical sub-network, communicationsfrom computing node A to computing node H are expected to first passthrough an initial intermediate destination of local router device Jbefore being forwarded to computing node H. Accordingly, since virtualrouter J is the initial intermediate destination for logically remotecomputing node H, the ARP message request 222-a includes the virtualnetwork address for virtual router J (i.e., “10.0.0.1”) and requests thecorresponding hardware address for virtual router J. In otherembodiments, computing node A may instead request virtual hardwareaddress information for computing node H directly (e.g., using thevirtual network address “10.1.5.3” for computing node H), but beprovided with the corresponding hardware address for virtual router J.

Communication Manager module R intercepts the ARP request 222-a, andobtains a hardware address to provide to computing node A as part ofspoofed ARP response message 222-b. The Communication Manager module Rmay determine the hardware address for virtual router J, as well as thatcomputing node H is part of a distinct logical sub-network fromcomputing node A, in various manners in various embodiments. Forexample, as previously discussed, the Communication Manager module R maystore various hardware address information as part of mappinginformation 212 c, and if so may already have stored hardware addressinformation for virtual router J and/or substrate network addressinformation for computing node H. If not, however, Communication Managermodule R performs one or more interactions 227 with the System Managermodule 290 to obtain information from the module 290 corresponding tothe indicated virtual network address for virtual router J. Rather thanobtaining a substrate network address corresponding to the indicatedvirtual network address, as for computing node G in FIG. 2A, the SystemManager module 290 indicates that the virtual network addresscorresponds to a virtual router device of the configured networktopology, and supplies a substrate network address that corresponds tothe final destination computing node H, and may also provide thehardware address information for virtual router J (e.g., by using theprovisioning information 292 and/or the network topology information296). In particular, the System Manager module 290 maintains variousinformation 296 related to the configured network topology for thevirtual computer networks that it provides or otherwise manages, such asinformation about specified networking devices, and uses thatinformation and the provisioning information 292 to provide requestedinformation to Communication Manager modules. The information 296 may insome embodiments be generated at least in part by a separate NetworkRouting Manager module (not shown), as described in greater detail withrespect to FIG. 2E and elsewhere. The Communication Manager module Rthen stores the received information as part of mapping information 212c for future use, and in this manner determines that computing node H ispart of a distinct sub-network from computing node A in the configurednetwork topology. Furthermore, Communication Manager module R providescomputing node A with the hardware address “00-01-42-09-88-73”corresponding to virtual router J as part of response message 222-b.While request 222-a and response message 222-b actually pass betweencomputing node A and Communication Manager module R in the mannerdiscussed, from the standpoint of computing node A, the communications222-a and 222-b are part of logical interactions 263 that occur withlocal router device J.

After receiving the response message 222-b from Communication Managermodule R, computing node A creates and initiates the sending of acommunication to computing node H, shown in FIG. 2C as communication222-c. In particular, the header of communication 222-c includes adestination network address for destination computing node H that is“10.1.5.3”, a destination hardware address that is the virtual hardwareaddress for virtual router J provided to computing node A in message222-b, a source network address for sending computing node A that is“10.0.0.2”, and a source hardware address for sending computing node Athat is an actual or dummy hardware address that was previouslyidentified to computing node A. From the standpoint of computing node A,the sent communication will be handled in the manner illustrated forlogical communication 265, and will be sent to local virtual router J ascommunication 265 a for forwarding based on the destination hardwareaddress in the communication. If virtual router J were physicallyimplemented and received such a communication 265 a, it would modify theheader of the communication 265 a and forward the modified communication265 b to virtual router L, which would similarly modify the header ofthe communication 265 b and forward that further modified communication265 c to computing node H. The modifications that virtual router J wouldperform to such a communication 265 a may include, for example,decrementing a TTL network hop value in the header and changing thedestination hardware address to correspond to the next destination,which in this example would be virtual router L. Similarly, themodifications that virtual router L would perform to such acommunication 265 b may include, for example, further decrementing theTTL network hop value in the header and changing the destinationhardware address to correspond to the next destination, which in thisexample would be computing node H. In some embodiments and situations,other similar modifications may be performed by the router devices ifthey were physically implemented and used for the forwarding of thecommunication.

While communication 222-c from computing node A to computing node H islogically handled in the manner illustrated for communication 265, thecommunication 222-c is actually intercepted and handled by CommunicationManager module R. In particular, in a manner similar to that describedin FIG. 2A for communication 220-c, Communication Manager module Rintercepts the communication 222-c, modifies the communication asappropriate, and forwards the modified communication over theinter-connection network 250 to computing node H. To determine thesubstrate network address to be used for forwarding the modifiedcommunication over the inter-connection network 250, CommunicationManager module R extracts the destination virtual network address anddestination virtual hardware address from the header of communication222-c. However, based on the destination virtual hardware addresscorresponding to virtual router J, Communication Manager module Rdetermines to use the destination virtual network address to identifythe destination substrate network address, in a manner different fromthat of FIG. 2A. Thus, the Communication Manager module R checks themapping information 212 c to determine if a substrate network addresscorresponding to computing node H's virtual network address has beenpreviously determined and stored. If not, Communication Manager module Rperforms one or more interactions 227 with the System Manager module 290to determine that information, in a manner similar to the interactions225 of FIG. 2A. As discussed in greater detail with respect to FIG. 2B,in response to the ARP request message 222-a and/or communication 222-c,the Communication Manager module R and/or the System Manager module 290may further perform various optional authentication activities.

After Communication Manager module R determines the IPv6 actual physicalsubstrate network address corresponding to computing node H, it createsa new IPv6 header that includes that actual physical substrate networkaddress as the destination address, and similarly adds a source IPv6address for computing node A to the new header. In this example, thephysical substrate network address corresponding to computing node H issimilar to that of computing node G, and in particular is the IPv6substrate network address “::0B:02:<Z-identifier>:10.1.5.3”, where“10.1.5.3” is stored in the last 32 bits of the 128-bit IPv6 address,and where “<Z-identifier>” is a 24-bit entity network identifier for themanaged virtual computer network. Thus, as with communications sent tocomputing node G, a communication sent over the inter-connection network250 to the substrate network address for computing node H will be routedto Communication Manager module S. The Communication Manager module Rnext creates a new communication 232-3 by modifying communication 222-cso as to replace the prior IPv4 header with the new IPv6 header (e.g.,in accordance with SIIT), including populating the new IPv6 header withother information as appropriate for the new communication (e.g.,payload length, traffic class packet priority, etc.), and forwardscommunication 232-3 over the inter-connection network 250. Theinter-connection network then uses the physical IPv6 destination networkaddress of the communication 232-3 to route the communication toCommunication Manager module S. When Communication Manager module Sreceives communication 232-3 via the inter-connection network 250, itperforms actions similar to those described in FIG. 2A with respect tocommunication 230-3, including to optionally perform interactions 242with the System Manager module 290 to determine if the communication isauthorized, to update mapping information 262 c to reflect any newinformation about computing node A, to modify the communication toinclude an appropriate IPv4 header, and to provide the modifiedcommunication as communication 247-e to computing node H.

Furthermore, as noted elsewhere, Communication Manager module R and/orCommunication Manager module S take further actions in this example tomodify the communication from computing node A to computing node H insuch a manner as to provide virtual networking functionalitycorresponding to the configured network topology for the virtualcomputer network, including to emulate functionality that would beprovided by virtual routers J and L if they were physically implementedfor the virtual computer network. For example, as previously discussed,virtual routers J and L would perform various modifications tocommunication 265 as it is forwarded to computing node H if thoserouters were physically implemented and used, including to modify TTLnetwork hop values and to perform other header modifications.Accordingly, Communication Manager module R and/or Communication Managermodule S may perform similar modifications to the communication 222-cand/or 247-e to emulate such functionality of the virtual routers J andL. Thus, computing node H receives a communication 247-e that appears tobe communication 265 c forwarded via the specified network topology forthe virtual computer network.

In this manner, the CNS system may provide virtual networkingfunctionality corresponding to the configured network topology, withoutany special configuration of the computing nodes of the managed virtualcomputer network or of the physical networking devices of theintervening substrate inter-connection network, based on theCommunication Manager modules overlaying the virtual computer network onthe actual physical inter-connection network in such a manner as toemulate the configured network topology. In addition, multiple modulesof the CNS system may operate together in a distributed manner toprovide functionality corresponding to a particular virtual networkingdevice, such as with modules 210, 260 and 290 operating together in theprevious example to emulate functionality corresponding to each ofvirtual router devices 270 a and 270 b.

FIG. 2D illustrates a further example of managing ongoing communicationsfor the virtual computer network described with respect to FIGS. 2A-2C,but with communications being managed to support virtual networkingfunctionality for the managed virtual computer network in accordancewith a configured network topology for the virtual computer network thatincludes one or more computing nodes of the virtual computer networkthat act as intermediate nodes that facilitate handling at least someinter-node communications. In particular, FIG. 2D illustrates computingnodes A and H, Communication Manager modules R and S, System Managermodule 290, and inter-connection network 250 in a manner similar to thatshown in FIGS. 2A-2C. However, in the example of FIG. 2D, the virtualcomputer network is configured to have at least two logical subnets, andcomputing node H is configured to act as an intermediate computing nodethrough which inter-node communications between the two logical subsetsare passed (e.g., as a firewall device between the two logical subnets).One or more specified networking devices may further be configured aspart of the network topology, such as illustrated with respect to FIG.2C, but are not illustrated or explicitly managed in the example of FIG.2D.

In the example of FIG. 2D, computing node A is sending a communicationto computing node C, with computing nodes A and C being configured tobelong to distinct logical subnets of the virtual computer network, andwith computing node H being configured to act as a firewall device forcommunications passing between those logical subnets. The actions of thephysically implemented modules 210 and 260 and devices of network 250 inactually sending the communication are shown, as well as the actions ofcomputing node H in facilitating the sending of the communication. Whileonly a single intermediate computing node is illustrated in FIG. 2D asbeing used in the routing path of the virtual computer network forinter-node communications between the two logical subnets, it will beappreciated that such a routing path may instead include 0 suchintermediate nodes (e.g., as discussed with respect to FIGS. 2A and 2B)or more than 1 such intermediate nodes in other situations, and thatsuch intermediate nodes may perform other types of actions in somesituations.

Thus, in a manner similar to that described with respect to FIG. 2A,computing node A determines to send a communication to computing node C,and accordingly exchanges various messages 224 with CommunicationManager module R 210. In particular, in this example, computing node Afirst sends a message request 224-a for virtual hardware addressinformation for computing node C. However, unlike the example of FIG. 2Ain which computing nodes A and G were part of the same logical subnetand did not include any intermediate computing nodes in the routing pathbetween computing nodes A and G for the virtual computer network,communications from computing node A to computing node C are configuredto first pass through an initial intermediate computing node H beforebeing forwarded to computing node G. Accordingly, the informationmaintained by the System Manager module 290 for use in directingcommunications from computing node A to computing node C reflects thatcomputing node H is an initial intermediate destination for suchcommunications.

Thus, Communication Manager module R intercepts the request 224-a, andobtains a hardware address to provide to computing node A as part ofspoofed ARP response message 224-b for use in directing the inter-nodecommunication along the configured routing path, in a manner similar tothat previously discussed. The Communication Manager module R may storevarious hardware address information as part of mapping information 212d, and if so may already have stored hardware address information foruse with communications from computing node A to computing node C. Ifnot, however, Communication Manager module R performs one or moreinteractions 229 with the System Manager module 290 to obtaininformation from the module 290 corresponding to the indicated virtualnetwork address for computing node C. Rather than providing thesubstrate network address corresponding to computing node C, however, asperformed for computing node G in FIG. 2A, the System Manager module 290instead indicates that the virtual network address for computing node C(at least for communications sent from computing node A) corresponds tothe substrate network address for computing node H as part of thesubstrate network routing path to computing node C, and may also provideinformation to the Communication Manager module R that indicates ahardware address to use to represent computing node C (at least forcommunications sent from computing node A). In particular, as discussedwith respect to FIG. 2C, the System Manager module 290 maintains variousinformation 296 related to the configured network topology for thevirtual computer networks that it provides or otherwise manages (e.g.,as generated at least in part by a separate Network Routing Managermodule, not shown, as described in greater detail with respect to FIG.2E and elsewhere), such as information about intermediate computingnodes along routing paths between particular computing nodes, and usesthat information to provide requested information to CommunicationManager modules. The Communication Manager module R then stores thereceived information as part of mapping information 212 d for futureuse, with the hardware address for computing node C being associatedwith the substrate network address for computing node H (at least forcommunications sent from computing node A), and provides computing nodeA with the hardware address corresponding to computing node C as part ofresponse message 224-b.

After receiving the response message 224-b from Communication Managermodule R, computing node A creates and initiates the sending of acommunication to computing node C, shown in FIG. 2D as communication224-c. In particular, the header of communication 224-c includes adestination network address for destination computing node C that is“10.0.5.1”, a destination hardware address that is the virtual hardwareaddress for computing node C provided to computing node A in message224-b, a source network address for sending computing node A that is“10.0.0.2”, and a source hardware address for sending computing node Athat is an actual or dummy hardware address that was previouslyidentified to computing node A.

The outgoing communication 224-c is intercepted and handled byCommunication Manager module R in a manner similar to that previouslydescribed with respect to FIGS. 2A and 2C. In particular, as withcommunication 220-c in FIG. 2A, Communication Manager module Rintercepts the communication 224-c, modifies the communication asappropriate, and forwards the modified communication over theinter-connection network 250 to computing node H. To determine thesubstrate network address to be used for forwarding the modifiedcommunication over the inter-connection network 250, CommunicationManager module R extracts the destination virtual network address anddestination virtual hardware address from the header of communication224-c. After Communication Manager module R determines the IPv6 actualphysical substrate network address corresponding to computing node H, itcreates a new IPv6 header that includes that actual physical substratenetwork address as the destination address, and similarly adds a sourceIPv6 address for computing node A to the new header. The CommunicationManager module R next creates a new communication 234-3 by modifyingcommunication 224-c so as to replace the prior IPv4 header with the newIPv6 header (e.g., in accordance with SOT), including populating the newIPv6 header with other information as appropriate for the newcommunication (e.g., payload length, traffic class packet priority,etc.), and forwards communication 234-3 over the inter-connectionnetwork 250. As discussed in greater detail with respect to FIG. 2B, inresponse to the request message 224-a and/or communication 224-c, theCommunication Manager module R and/or the System Manager module 290 mayfurther perform various optional authentication activities.

The inter-connection network then uses the physical IPv6 destinationnetwork address of the communication 234-3 to route the communication toCommunication Manager module S. When Communication Manager module Sreceives communication 234-3 via the inter-connection network 250, itperforms actions similar to those described in FIG. 2A with respect tocommunication 230-3, including to optionally perform interactions 244with the System Manager module 290 to determine if the communication isauthorized, to update mapping information 262 d to reflect any newinformation about computing node A, to modify the communication toinclude an appropriate IPv4 header, and to provide the modifiedcommunication as communication 248-e to computing node H. However, thecommunication 248-e provided to computing node H includes informationthat indicates that computing node C is the final destination for thecommunication, such as for use by computing node H in performing itsfirewall analysis. In particular, in this example, the communication248-e includes a destination hardware address that corresponds tocomputing node H, but the destination network address is the virtualnetwork address for computing node C, in a manner similar tocommunication 222-c/265 a of FIG. 2C.

When computing node H receives communication 248-e, it optionallyperforms various firewall-related activities for the communication,based on its configuration, and in this example determines to forwardthe communication on to its final destination of computing node C. Asdiscussed in greater detail elsewhere, such intermediate computing nodesvia which some inter-node communications may be directed may provide avariety of other types of capabilities in other embodiments andsituations. Furthermore, as noted elsewhere, computing node H may insome such situations determine to modify the communication in one ormore manners based on its firewall policies. In order to forward thecommunication on to computing node C, computing node H updates thereceived communication 248-e so that it has a new destination hardwareaddress that corresponds to computing node C (optionally afterperforming interactions with Communication Manager module S to obtainthe hardware address for computing node C's virtual network address, notshown, in a manner similar to that of communications 224-a and 224-b).The computing node H then sends the modified communication as outgoingcommunication 248-f.

In a manner similar to that previously discussed elsewhere, the outgoingcommunication 248-f is intercepted and handled by Communication Managermodule S. In particular, Communication Manager module S intercepts thecommunication 248-f, modifies the communication as appropriate, andforwards the modified communication over the inter-connection network250 to computing node C. To determine the substrate network address tobe used for forwarding the modified communication over theinter-connection network 250, Communication Manager module S extractsthe destination virtual network address and destination virtual hardwareaddress from the header of communication 248-f. After CommunicationManager module S determines the IPv6 actual physical substrate networkaddress corresponding to computing node C, it creates a new IPv6 headerthat includes that actual physical substrate network address as thedestination address, and similarly adds a source IPv6 address forcomputing node A to the new header. The Communication Manager module Snext creates a new communication 234-6 by modifying communication 248-fso as to replace the prior IPv4 header with the new IPv6 header (e.g.,in accordance with SIIT), including populating the new IPv6 header withother information as appropriate for the new communication (e.g.,payload length, traffic class packet priority, etc.), and forwardscommunication 234-6 over the inter-connection network 250.

The inter-connection network then uses the physical IPv6 destinationnetwork address of the communication 234-6 to route the communication toCommunication Manager module R. When Communication Manager module Rreceives communication 234-6 via the inter-connection network 250, itperforms actions similar to those previously described, including tooptionally determine if the communication is authorized, to modify thecommunication to include an appropriate IPv4 header, and to provide themodified communication as communication 224-h to computing node C. Asdiscussed in greater detail elsewhere, in other embodiments thesubstrate network that is used may instead use the same networkaddressing scheme as the overlay virtual computer network, such as toboth use IPv4.

In this manner, the CNS system may provide virtual networkingfunctionality corresponding to the configured network topology,including to support intermediate computing nodes along routing pathsbetween particular computing nodes, and again without any specialconfiguration of the computing nodes of the managed virtual computernetwork or of the physical networking devices of the interveningsubstrate inter-connection network, based on the Communication Managermodules overlaying the virtual computer network on the actual physicalinter-connection network in such a manner as to emulate the configurednetwork topology.

FIG. 2E continues the example of FIG. 2D, in which computing node Hacted as an intermediate computing node for at least some inter-nodecommunications of a managed virtual computer network by facilitatinghandling of those communications, and in particular performedfirewall-related functionality for such communications as part of theexample of FIG. 2D. In the example of FIG. 2E, computing node Hcontinues to act as such an intermediate computing node for at leastsome inter-node communications, and is further configured to participatein one or more defined routing protocols for the managed virtualcomputer network, such as to exchange routing-related communicationswith other specified networking devices of the managed virtual computernetwork that include routing information for the managed virtualcomputer network. Such other specified networking devices of the managedvirtual computer network may include, for example, virtual routerdevices 270 a and 270 b, as discussed in greater detail with respect toFIG. 2C.

Accordingly, in the example of FIG. 2E, computing node H has determinedto send a routing-related communication to virtual router L 270 b (e.g.,based on virtual router L being configured in the network topology forthe managed virtual computer network as being a nearby neighbor router,or instead in other manners), such as to include various routinginformation for the managed virtual computer network that is locallystored by or otherwise accessible to computing node H. Thus, in thisexample, computing node H creates the routing-related communication, andinitiates sending of the routing-related communication 269-j, whichcomputing node H intends to send directly to virtual router L as shownwith respect to logical communication 266. In particular, therouting-related communication has a destination network address anddestination hardware address that are the virtual network address andvirtual hardware address assigned to virtual router L (in this example,“10.1.5.1” and “00-01-42-CD-11-01,” respectively), and source networkaddress and source hardware address corresponding to computing node H.While not illustrated here, in order to obtain the destination networkaddress and/or the destination hardware address for virtual router L,computing node H may perform one or more other prior communications (notshown) to obtain such information, such as via an ARP message request.

In a manner similar to that described previously, Communication Managermodule S intercepts the routing-related communication 269-j, anddetermines that the routing-related communication is intended for avirtual networking device that is part of the configured networktopology of the managed virtual computer network, such as based on theindicated destination virtual network address and/or destinationhardware address of the routing-related communication, or instead inother manners (e.g., based at least in part on the routing protocol usedfor the communication). As previously discussed, the CommunicationManager module S may store various hardware address information andvirtual network address information as part of mapping information 262e, and if so may already have stored information for use withcommunications directed to virtual router L. If not, however,Communication Manager module S may perform one or more interactions (notshown) with the System Manager module 290 to obtain information from themodule 290 corresponding to the virtual router L, in a manner similar tothat discussed previously.

However, in a manner different from that of FIGS. 2A-2D, rather thanforwarding the received communication 269-j over the substrate networkto its intended destination, Communication Manager module S determinesto provide the received routing-related communication 269-j (or routinginformation from the communication) to the Network Routing Managermodule 295, such as via one or more interactions 243 e. While the module295 is not explicitly illustrated as being physically connected to theinter-connection network 250 in this example, such physical connectionsmay exist in at least some embodiments, in a manner similar to that forSystem Manager module 290 and the various Communication Manager modules.Accordingly, while the interactions 243 e with the module 295 are notillustrated in this example as explicitly traveling over theinter-connection network 250, it will be appreciated that suchinteractions may include one or more communications that do travel overthe inter-connection network 250 in at least some embodiments. Inaddition, as discussed in greater detail elsewhere, in some embodiments,the Communication Manager module S and/or the Network Routing Managermodule 295 may filter or restrict at least some types of routing-relatedcommunications, such as by discarding or otherwise not using suchcommunications, and thus the Communication Manager module S and/or theNetwork Routing Manager module 295 may further perform various optionalactivities in determining whether to use the routing information in thereceived communication 269-j.

As discussed in greater detail elsewhere, the Network Routing Managermodule 295 may use the routing information from the routing-relatedcommunication in various manners, including to determine whether therouting information indicates any changes in the configured networktopology for the managed virtual computer network. As previously noted,the System Manager module 290 maintains various information 296 relatedto the configured network topology for the virtual computer networksthat it provides or otherwise manages (e.g., as generated at least inpart by the Network Routing Manager module 295), such as informationabout intermediate computing nodes along routing paths betweenparticular computing nodes, and uses that information to providerequested information to Communication Manager modules. Accordingly, theNetwork Routing Manager module 295 may analyze the received routinginformation to determine if it reflects any relevant changes to theconfigured network topology information for the managed virtual computernetwork (e.g., any changes regarding intermediate computing nodes alongparticular inter-node communication routing paths). If the NetworkRouting Manager module 295 identifies any such relevant changes to theconfigured network topology information for the managed virtual computernetwork, the Network Routing Manager module 295 performs one or moreinteractions 297 e (optionally by sending one or more communications,not shown, over the inter-connection network 250) with the SystemManager module 290 to cause the network topology information 296 to beupdated in a corresponding manner.

In a similar manner, after the managed virtual computer network is inthe use, the entity Z client 285 associated with the managed virtualcomputer network may optionally in some embodiments perform additionalinteractions with the System Manager module 290 to provide updates orother new configured network topology information for the managedvirtual computer network. If so, the System Manager module 290 mayprovide the new network topology information to the Network RoutingManager module 295 (e.g., via one or more interactions 297 e). If so,the Network Routing Manager module 295 may proceed to perform actionssimilar to those performed for the received routing information fromrouting-related communication 269-j, including to analyze the receivednew network topology information to determine if it reflects anyrelevant changes to the configured network topology information for themanaged virtual computer network. If the Network Routing Manager module295 identifies any such relevant changes to the configured networktopology information for the managed virtual computer network, theNetwork Routing Manager module 295 similarly performs one or moreinteractions 297 e with the System Manager module 290 to cause thenetwork topology information 296 to be updated in a correspondingmanner.

In addition to updating the stored network topology information 296 asappropriate, the Network Routing Manager module 295 may further takeother actions in some embodiments. For example, if changes to thenetwork topology are detected that reflect changes to one or moreintermediate computing nodes for use in inter-node communicationsbetween at least some computing nodes, the Network Routing Managermodule 295 may optionally perform interactions 246 to supplycorresponding update information to one or more Communication Managermodules that manage computing nodes affected by the network topologychanges. If such updated information is supplied to CommunicationManager modules R and/or S, for example, they may use that updatedinformation to update their stored mapping information 212 e and 262 e,respectively, in a corresponding manner for use with future inter-nodecommunications that are affected by the network topology change. Inother embodiments, the Communication Manager modules may instead obtainsuch updated network topology information directly from the SystemManager module 290, such as if the Communication Manager modulesperiodically contact the System Manager module 290 for currentinformation (e.g., if the stored mapping information 212 e and 262 eexpires periodically or instead based on other criteria, such as basedon a communication from the System Manager module 290 and/or the NetworkRouting Manager module 295 that some or all of the stored mappinginformation is no longer valid).

Furthermore, while not illustrated in FIG. 2E, the Network RoutingManager module 295 may take other actions in at least some embodimentsand situations, such as to initiate the sending of routing-relatedcommunications to computing nodes such as computing node H thatparticipate in the predefined routing protocol for the managed virtualcomputer network. Such sending of a routing-related communication tocomputing node H or other similar computing node may be initiated by theNetwork Routing Manager module 295 in various manners in variousembodiments, such as by generating a particular routing-relatedcommunication and forwarding it over the inter-connection network 250 tothe destination computing node in a manner similar to that of otherinter-node communications (optionally with the sent communicationincluding sender information corresponding to a virtual networkingdevice for the managed virtual computer network, such as virtual routerL or virtual router J). Alternatively, the Network Routing Managermodule 295 may in some embodiments and situations instead provide therouting information intended for such a computing node to the computingnode's associated Communication Manager module (e.g., to CommunicationManager module S for computing node H), and have that associatedCommunication Manager module generate and provide an appropriaterouting-related communication to the associated computing node. Asdiscussed in greater detail elsewhere, such routing information providedto computing nodes may have various forms, including the following:routing information received from other computing nodes or other sources(e.g., a remote networking device at a client's remote network thatinteracts with the managed virtual computer network) that is beingforwarded to additional computing nodes; routing information thatreflects changes made by the client to the configured network topologyfor the managed virtual computer network, such as via interactions withthe System Manager module; routing information that is generated by theNetwork Routing Manager module to provide globally consistent routinginformation for all computing nodes of the managed virtual computernetwork, or that otherwise satisfies a centralized goal for operation ofthe managed virtual computer network; etc.

In this manner, the CNS system may further provide virtual networkingfunctionality corresponding to the configured network topology,including to support intermediate computing nodes along routing pathsbetween particular computing nodes, and again without any specialconfiguration of the computing nodes of the managed virtual computernetwork or of the physical networking devices of the interveningsubstrate inter-connection network. Such techniques may be based atleast in part on the Communication Manager modules managing at leastsome routing-related communications (e.g., routing-relatedcommunications directed to virtual networking devices) in appropriatemanners, and/or on a Network Routing Manager module using configurednetwork topology information and/or dynamically supplied routinginformation to manage inter-node communications for a managed virtualcomputer network.

FIG. 2F continues the examples of FIGS. 2A-2E, and further illustratesadditional details regarding supporting connections between multiplemanaged computer networks. In particular, FIG. 2F illustrates computingnode A 205 a, the logical representation 270 a of virtual router J,Communication Manager modules R and S 210 and 260, System Manager module290, Network Routing Manager module 295, and inter-connection network250 in a manner similar to that shown in various of FIGS. 2A-2E.However, FIG. 2F further illustrates additional components, includingcomputing node I 255 c that is associated with Communication Managermodule S and is part of a second managed virtual computer networkprovided to client entity Y (along with other computing nodes, such ascomputing node B 205 b illustrated in FIG. 2A), as well as a logicalrepresentation 270 d of virtual router device M that is also part of theconfigured network topology for the second virtual computer networkprovided to client entity Y (but that is not actually physicallyimplemented as part of providing the managed second virtual computernetwork). In addition, a logical representation 215 of a virtual peeringrouter device is also illustrated, such as to provide a logicalconnection between the virtual router J of the first virtual computernetwork for entity Z and the virtual router M of the second virtualcomputer network for entity Y, as described below, although in otherembodiments the two (or more) virtual computer networks may instead beinterconnected in other manners (e.g., via multiple connected virtualpeering routers). In this example, the single virtual peering router hasinterfaces (not shown) for each of the two virtual computer networks,such as by being assigned the network address of “10.0.0.9” for a firstinterface for the first virtual computer network for entity Z, and thenetwork address of “20.0.7.9” for a second interface for the secondvirtual computer network for entity Y. As discussed in greater detailelsewhere, the virtual peering router is not actually physicallyimplemented, in a manner similar to virtual routers J and M of the firstand second managed virtual computer networks, but various modules of theconfigurable network service operate together to emulate functionalitycorresponding to the virtual peering router.

In particular, in this example, entities Z and Y have previously eachconfigured their virtual computer network to connect to the virtualpeering router 215, so as to enable communications to pass at least fromthe first virtual computer network for entity Z to the second virtualcomputer network for entity Y (and optionally from the second virtualcomputer network to the first virtual computer network as well). Inaddition, while not illustrated here, one or more routing communicationsmay have optionally been directed to the virtual peering router 215 fromeach of the two virtual computer networks, in a manner similar to thatpreviously discussed with respect to FIG. 2E. Once the two virtualcomputer networks are connected to the virtual peering router 215 andconfigured to enable communications from at least the first virtualcomputer network to the second virtual computer network, the NetworkRouting Manager module 295 updates the network topology information 296that is accessible to the System Manager module 290 to reflect thatconfiguration, as well as in light of any peering configurationinformation specified by entities Y and/or Z. For example, the updatednetwork topology information 296 may include information to indicatethat the computing nodes of the second virtual computer network (such ascomputing nodes B and I) are accessible from the computing nodes of thefirst virtual computer network (such as computing nodes A, C, G, H,etc.). In addition, the Network Routing Manager module 295 and/or theSystem Manager module 290 may further take actions in some embodimentsto update corresponding mapping information stored by CommunicationManager modules associated with computing nodes of the first virtualcomputer network, such as to update mapping information 212 f used byCommunication Manager module R.

In the example of FIG. 2F, computing node A of the first virtualcomputer network is sending a communication to computing node I of thesecond virtual computer network, and the actions of the physicallyimplemented modules 210 and 260 and devices of network 250 in actuallysending the communication are shown, as well as emulated actions of thevirtual routers 270 a, 270 d and 215 in logically sending thecommunication. As discussed previously with respect to FIG. 2C, virtualrouter device J 270 a may be a local router device to computing node Ain the configured network topology for the first virtual computernetwork (e.g., may manage a first sub-network that includes computingnode A), and virtual router device M 270 d may similarly be a localrouter device to computing node I in the configured network topology ofthe second virtual computer network. While computing nodes A and I areillustrated as being separated by two router devices of the two managedvirtual computer networks in the configured network topology in thisexample, it will be appreciated that two such computing nodes may beseparated by other numbers of logical router devices in othersituations, and that other types of networking devices may separatecomputing nodes in some situations. In addition, while FIG. 2C includesdetails regarding how hardware addresses may be assigned to computingnodes and virtual routers, and used to direct communications, suchdetails are not included in FIG. 2F for the sake of brevity.

In a manner similar to that described with respect to other figures,such as FIGS. 2A and 2C, computing node A determines to send acommunication to computing node I, and accordingly exchanges variousmessages 226 with Communication Manager module R 210. In particular, inthis example, computing node A first sends a message request 226-a forvirtual hardware address information of computing node I. In a mannersimilar to that of FIG. 2C, communications from computing node A tocomputing node I are expected to first pass through an initialintermediate destination of local router device J before beingeventually forwarded to computing node I. Accordingly, since virtualrouter J is the initial intermediate destination for logically remotecomputing node I, the message request 226-a includes the virtual networkaddress for virtual router J (i.e., “10.0.0.1”) and requests thecorresponding hardware address for virtual router J. In otherembodiments, computing node A may instead request virtual hardwareaddress information for computing node I directly (e.g., using thevirtual network address “20.0.0.3” for computing node I), but beprovided with the corresponding hardware address for virtual router J.

Communication Manager module R intercepts the request 226-a, and obtainsa hardware address to provide to computing node A as part of spoofedresponse message 226-b. The Communication Manager module R may determinethe hardware address for virtual router J, as well as that computingnode I is part of a distinct virtual computer network from computingnode A, in various manners in various embodiments. For example, aspreviously discussed, the Communication Manager module R may storevarious address information as part of mapping information 212 f, and ifso may already have stored hardware address information for virtualrouter J and/or a substrate network address that corresponds tocomputing node I. If not, however, Communication Manager module Rperforms one or more interactions 228 with the System Manager module 290to obtain information from the module 290 corresponding to the indicatedvirtual network address for virtual router J. Rather than obtaining asubstrate network address corresponding to the indicated virtual networkaddress, as for computing node G in FIG. 2A, the System Manager module290 indicates that the virtual network address corresponds to a virtualrouter device of the configured network topology for the first virtualcomputer network, and supplies a substrate network address thatcorresponds to the final destination computing node I, and may alsoprovide the hardware address information for virtual router J (e.g., byusing the network topology information 296 and/or the provisioninginformation 292). The Communication Manager module R then stores thereceived information as part of mapping information 212 f for futureuse, and in this manner determines that computing node I is part of adistinct virtual computer network from computing node A. Furthermore,Communication Manager module R provides computing node A with a hardwareaddress corresponding to virtual router J as part of response message226-b. While request 226-a and response message 226-b actually passbetween computing node A and Communication Manager module R in themanner discussed, from the standpoint of computing node A, thecommunications 226-a and 226-b are part of logical interactions 264 thatoccur with local router device J.

After receiving the response message 226-b from Communication Managermodule R, computing node A creates and initiates the sending of acommunication to computing node I, shown in FIG. 2F as communication226-c. In particular, the header of communication 226-c includes adestination network address for destination computing node I that is“20.0.0.3”, a destination hardware address that is the virtual hardwareaddress for virtual router J provided to computing node A in message226-b, a source network address for sending computing node A that is“10.0.0.2”, and a source hardware address for sending computing node Athat is an actual or dummy hardware address that was previouslyidentified to computing node A. From the standpoint of computing node A,the sent communication will be handled in the manner illustrated forlogical communication 267, and will be sent to local virtual router J ascommunication 267 a for forwarding based on the destination hardwareaddress in the communication. If virtual router J were physicallyimplemented and received such a communication 267 a, it would modify theheader of the communication 267 a (as discussed in greater detail withrespect to FIG. 2C) and forward the modified communication 267 b tovirtual peering router 215 using its assigned network address of“10.0.0.9” for the first virtual computer network, which would similarlymodify the header of the communication 267 b and forward that furthermodified communication 267 c to virtual router M, which would similarlymodify the header of the communication 267 c and forward that furthermodified communication 267 d to computing node I.

While communication 226-c from computing node A to computing node I islogically handled in the manner illustrated for communication 267, thecommunication 226-c is actually intercepted and handled by CommunicationManager module R. In particular, in a manner similar to that describedin FIG. 2C for communication 222-c, Communication Manager module Rintercepts the communication 226-c, modifies the communication asappropriate, and forwards the modified communication over theinter-connection network 250 to computing node I. To determine thesubstrate network address to be used for forwarding the modifiedcommunication over the inter-connection network 250, CommunicationManager module R extracts the destination virtual network address anddestination virtual hardware address from the header of communication226-c. Based on the destination virtual hardware address correspondingto virtual router J, Communication Manager module R determines to usethe destination virtual network address to identify the destinationsubstrate network address. Thus, the Communication Manager module Rchecks the mapping information 212 f to determine if a substrate networkaddress corresponding to computing node l's virtual network address hasbeen previously determined and stored. If not, Communication Managermodule R performs one or more interactions 228 with the System Managermodule 290 to determine that information, in a manner similar to theinteractions 227 of FIG. 2C. As discussed in greater detail previously,in response to the request message 226-a and/or communication 226-c, theCommunication Manager module R and/or the System Manager module 290 mayfurther perform various optional authentication activities beforeforwarding the communication to the final destination of computing nodeI, including to verify that peering configuration information specifiedby entity Z (if any) and by entity Y (if any) authorizes computing nodeA to send communications to computing node I.

After Communication Manager module R determines the IPv6 actual physicalsubstrate network address corresponding to computing node I, it createsa new IPv6 header that includes that actual physical substrate networkaddress as the destination address, and similarly adds a source IPv6address for computing node A to the new header. In this example, thephysical substrate network address corresponding to computing node I issimilar to that of computing nodes G and H, and in particular is theIPv6 substrate network address “::0B:02:<Y-identifier>:20.0.0.3”, where“20.0.0.3” is stored in the last 32 bits of the 128-bit IPv6 address,and where “<Y-identifier>” is a 24-bit entity network identifier for thesecond managed virtual computer network for entity Y. The CommunicationManager module R next creates a new communication 237-3 by modifyingcommunication 226-c so as to replace the prior IPv4 header with the newIPv6 header (e.g., in accordance with SIIT), including populating thenew IPv6 header with other information as appropriate for the newcommunication (e.g., payload length, traffic class packet priority,etc.), and forwards communication 237-3 over the inter-connectionnetwork 250. The inter-connection network then uses the physical IPv6destination network address of the communication 237-3 to route thecommunication to Communication Manager module S. When CommunicationManager module S receives communication 237-3 via the inter-connectionnetwork 250, it performs actions similar to those described in FIG. 2Cwith respect to communication 232-3, including to optionally performinteractions 241 with the System Manager module 290 to determine if thecommunication is authorized, to update mapping information 262 f toreflect any new information about computing node A, to modify thecommunication to include an appropriate IPv4 header, and to provide themodified communication as communication 249-e to computing node I.

Furthermore, as noted elsewhere, Communication Manager module R and/orCommunication Manager module S take further actions in this example tomodify the communication from computing node A to computing node I insuch a manner as to provide virtual networking functionalitycorresponding to the managed virtual computer networks, including toemulate functionality that would be provided by virtual routers J and Mand virtual peering router 215 if they were physically implemented. Forexample, as previously discussed, virtual routers J and M would performvarious modifications to communication 267 as it is forwarded tocomputing node I if those routers were physically implemented and used,including to modify TTL network hop values and to perform other headermodifications. Accordingly, Communication Manager module R and/orCommunication Manager module S may perform similar modifications to thecommunication 226-c and/or 249-e to emulate such functionality of thevirtual routers J and M. Thus, computing node I receives a communication249-e that appears to be communication 267 d forwarded via the virtualpeering router and the specified network topology for the second virtualcomputer network.

In addition, in some embodiments, additional actions may be taken tosupport inter-connections between multiple managed virtual computernetworks. For example, if the second virtual computer network for entityY had instead been configured to have overlapping network addresses withthose of the first virtual computer network for entity Z, the variousmodules of the configurable network service may in some embodiments beconfigured to perform additional actions to support inter-operability ofthe two managed virtual computer networks. For example, if computingnode I had instead been configured to use the virtual network address of“10.0.0.3” for the second virtual computer network, it would share thatvirtual network address with computing node G of the first virtualcomputer network—accordingly, if computing node A had directed itsoutgoing communication to that virtual network address, thecommunication would have been routed to computing node G rather than tocomputing node I. Thus, in some embodiments, the configurable networkservice may take actions to prevent such overlaps in virtual networkaddresses between connected managed virtual computer networks, such asto provide functionality analogous to that of network addresstranslation (“NAT”). If computing node I of the second virtual computernetwork had been configured to share the virtual network address of“10.0.0.3” with existing computing node G of the first virtual computernetwork, for example, the configurable network service may select a newvirtual network address to represent computing node I that does notoverlap with the virtual network addresses of the first virtual computernetwork (e.g., to use the new virtual network address of “210.0.0.3”.Accordingly, the information that is provided to the first virtualcomputer network for the second virtual computer network would includeany such representative network addresses, and computing node A wouldinstead direct its outgoing communication 226-c to the destinationvirtual network address of “210.0.0.3”. In other embodiments, theconfigurable network service may instead handle overlapping networkaddresses between inter-connected managed virtual computer networks inother manners, such as to not allow such managed virtual computernetworks to be inter-connected, and may further optionally notify theclients associated with one or more such managed virtual computernetworks of the overlap that prevents the inter-connection (e.g.,optionally with a new suggested virtual network address range to be usedfor at least one of the managed virtual computer networks that will notoverlap with the virtual network addresses used by the other managedvirtual computer network(s)).

In addition, while the previous example of FIG. 2F involved acommunication that was sent from the first virtual computer network tothe second virtual computer network, it will be appreciated that thesecond virtual computer network may be configured in at least someembodiments to similarly send communications to the first virtualcomputer network (e.g., any communication; only responses tocommunications from the first virtual computer network, such as toenable computing node I to respond to computing node A but not to send anew communication to computing node G; etc.). Such authorizedcommunications from a computing node of the second virtual computernetwork to one or more computing nodes of the first virtual computernetwork will similarly be logically directed through the virtual peeringrouter 215, but in actuality will be passed directly to the destinationcomputing node via the substrate inter-connection network 250.Furthermore, as discussed in greater detail elsewhere, in someembodiments a client may configure one or more computing nodes of theirmanaged virtual computer network to operate as a network appliance, suchas to provide one or more types of functionality for communications thatare routed through those computing nodes (e.g., for software firewallcomputing node H of FIG. 2D). In some embodiments, one or more clientswho configure their managed virtual computer network to connect to avirtual peering router may configure one or more such network appliancecomputing nodes to be used to manage communications that are receivedfrom and/or sent to the virtual peering router. Thus, if entity Y hadconfigured computing node B to act as a firewall for any incomingcommunications to the second virtual computer network from the firstvirtual computer network, for example, the communication from computingnode A to computing node I would have first been routed to computingnode B for handling, before optionally being forwarded to computing nodeI, in a manner similar to that described for software firewall computingnode H of FIG. 2D. Alternatively, the configurable network service mayenable a client to specify one or more filters or other communicationconstraints that the virtual peering router is to enforce for computingnode communications and/or routing communications sent via theconnection between the client's managed virtual computer network and thevirtual peering router, and the various modules of the configurablenetwork service may enforce such constraints as part of authorizingwhether to forward communications between computing nodes.

Furthermore, while not illustrated with respect to FIG. 2F, in someembodiments routing communications may be directed to the virtualpeering router 215 from one or both of the managed virtual computernetworks provided to entities Z and Y, such as from computing nodes ofthose managed computer networks that participate in the routingprotocols used by those managed virtual computer networks. Furthermore,the various managed computer networks that are connected to a virtualpeering router may in some embodiments and situations use multipledistinct routing protocols. When such routing communications arereceived, they may be handled in a manner similar to that illustratedwith respect to FIG. 2E, such as for a communication manager module thatreceives such a routing communication to forward it to the NetworkRouting Manager module 295 for further processing. Similarly, while alsonot illustrated with respect to FIG. 2F, the Network Routing Managermodule 295 (or other CNS modules) may send one or more such routingcommunications to the other of the managed virtual computer networksprovided to entities Z and Y, if any specified peering configurationinformation for the virtual peering router 215 authorizes suchforwarding, such as to provide that other managed virtual computernetwork with information about computing nodes of the other managedvirtual computer network that are accessible via the virtual peeringrouter 215 (e.g., for computing nodes of those managed virtual computernetworks that participate in the routing protocol for that managedvirtual computer network).

In addition, while the example of FIG. 2F involved a communication thatwas sent from a first computing node associated with a firstcommunication manager module (i.e., from computing node A associatedwith Communication Manager module R) to a second computing nodeassociated with a distinct second communication manager module (i.e., tocomputing node I associated with Communication Manager module S), inother situations a communication may be sent between two computing nodesof two distinct virtual computer networks that are associated with asingle communication manager module. For example, computing node A ofthe first virtual computer network may instead send a communication tocomputing node B 205 b of the second virtual computer network, with bothcomputing nodes A and B being associated with Communication Managermodule R (as discussed in greater detail with respect to FIG. 2A). Insuch situations, the communication will be handled in a manner similarto that described in FIG. 2F, but that single associated communicationmanager module may manage the forwarding of the communication betweenthe computing nodes without forwarding a copy of the communication overthe inter-connection network 250, in a manner similar to that discussedpreviously.

In this manner, the CNS system may provide virtual networkingfunctionality corresponding to the configured network topology, withoutany special configuration of the computing nodes of the managed virtualcomputer network or of the physical networking devices of theintervening substrate inter-connection network, based on theCommunication Manager modules overlaying the virtual computer network onthe actual physical inter-connection network in such a manner as toemulate the configured network topology. In addition, multiple modulesof the CNS system may operate together in a distributed manner toprovide functionality corresponding to a particular virtual networkingdevice, such as with modules 210, 260 and 290 operating together in theprevious example to emulate functionality corresponding to each ofvirtual router devices 270 a and 270 b.

In addition, while the example of FIG. 2F involves an inter-connectionbetween two managed computer networks that are provided to clients, inother embodiments the configurable network service may provide othertypes of inter-connections for managed computer networks. As oneexample, the configurable network service may provide one or morespecialized managed computer networks that each provides one or moreparticular types of functionality that may be of use to managed computernetworks provided to clients, and the configurable network service mayenable particular clients to elect to connect their managed computernetworks to one or more such specialized computer networks in order toreceive the type(s) of functionality provided by those specializedcomputer network(s). For example, the configurable network service mayprovide a specialized managed computer network that provides access tothe Internet or other computer systems external to the configurablenetwork service, optionally with various functionality to analyzecommunications that are received and/or sent (e.g., firewallcapabilities; intrusion detection system capabilities; intrusionprevention system capabilities; WAN acceleration capabilities; spamfiltering capabilities; etc). Accordingly, if a particular client wouldlike their managed virtual computer network to have interconnectivitywith such external computer systems, but does not want to manage thevarious functionality to analyze incoming and/or outgoingcommunications, the client may configure their managed virtual computernetwork to be connected to such a specialized managed virtual computernetwork, such as by connecting to a virtual peering router created bythe specialized managed virtual computer network. It will be appreciatedthat a variety of other types of functionality may similarly be providedby other such specialized managed computer networks.

Furthermore, as previously noted, the configurable network service mayin some embodiments operate as a fee-based service, such that clientsare customers that pay fees to the configurable network service. In suchembodiments, the configurable network service may charge clients usingvarious metrics and for various types of functionality that is provided.As one example, in embodiments in which the configurable network serviceprovides specialized managed computer networks, the configurable networkservice may charge clients one or more fees for connecting to and/orotherwise using such a specialized managed computer network. Moregenerally, clients may be charged for connecting to and/or using anyvirtual peering router, including virtual peering routers that connecttwo or more managed computer networks provided to clients. Other metricson which fees may be based in at least some embodiments include, forexample, one or more of the following: connecting to a virtual peeringrouter; based on an amount of traffic sent and/or received via a virtualpeering router; based on an amount of time that a virtual peering routeris connected to or otherwise used; based on a quantity or rate ofrouting changes or other routing-related communications that are sent toor via a virtual peering router; based on a quantity or rate of routingchanges or other routing-related communications that are received fromor via a virtual peering router; based on the types of communicationsthat are sent via a virtual peering router, including for various typesof announcements or specialized types of communications (e.g., anycastcommunications, broadcast communications, etc.); for a virtual peeringrouter to enforce client-specified routing filters or other specifiedrestrictions on types of communications that are allowed or disallowed;for a virtual peering router to provide NAT functionality to manageinter-connections between two or more managed computer networks; etc.Furthermore, fees that are charged may have various forms, includingone-time fees, ongoing subscription fees (e.g., with a certain fee for aspecified period of time), usage-based fees (e.g., to vary with anamount of use of a particular type), etc.

In addition, the configurable network service may in some embodimentsspecify or enforce other types of restrictions on the use of virtualpeering routers, whether instead of or in addition to fee-basedrestrictions. For example, a first client that initiates the creation orother providing of a virtual peering router for a managed computernetwork of the client, such as to enable other managed computer networksto inter-communicate with the first client's managed computer network,may specify various restrictions on the use that virtual peering router.Such restrictions may have various forms, including, for example, one ormore of the following: restrictions on times when the virtual peeringrouter is available; restrictions on an amount of time that a managedcomputer network may be connected to the virtual peering router;restrictions on particular clients or managed computer networks that mayconnect to the virtual peering router; etc. In other embodiments, eachclient who has a managed computer network connected to a virtual peeringrouter may specify at least some types of restrictions regarding use ofthe virtual peering router (e.g., with respect to how/when/whether othermanaged computer networks may communicate with the client's managedcomputer network), and/or the configurable network service may specifyat least some types of restrictions for at least some virtual peeringrouters (e.g., based on fees paid by the client(s) whose managedcomputer networks are connected to the virtual peering router, such asif the configurable network service provides different types of virtualpeering routers or different types of capabilities for different fees;based on policies specified by the configurable network service for someor all virtual peering routers; etc.).

Thus, in this manner, the CNS system may further provide virtualnetworking functionality corresponding to configured network topologiesand inter-connections, including in the manners discussed with respectto FIG. 2F to support connections between multiple managed computernetworks via virtual peering router functionality provided by the CNSsystem. As previously noted, such virtual networking functionality maybe provided without any special configuration of the computing nodes ofthe managed virtual computer networks or of the physical networkingdevices of the intervening substrate inter-connection network, such asbased at least in part on the Communication Manager modules managingcommunications in appropriate manners, and/or on a Network RoutingManager module using configured network topology information and/ordynamically supplied routing information to handle communications for amanaged virtual computer network.

In addition, as previously noted, various computing nodes may beselected for a managed virtual computer network and configured inaccordance with a configured network topology of that managed virtualcomputer network in various manners. For example, in some embodiments,the selection of a computing node to be used in a managed virtualcomputer network and/or to be assigned a particular role in a configurednetwork topology may be based at least in part on a geographical and/ornetwork location of the computing node, such as an absolute location, orinstead a location relative to one or more other computing resources ofinterest (e.g., other computing nodes of the same managed virtualcomputer network, storage resources to be used by the computing node,etc.), such as within a minimum and/or maximum specified geographicaldistance or other degree of proximity to an indicated other computingresource or other location. In addition, in some embodiments, factorsused when selecting a computing node may be based in part or in whole onfactors other than location, such as to include one or more of thefollowing: constraints related to capabilities of a computing node, suchas resource-related criteria (e.g., an amount of memory, an amount ofprocessor usage, an amount of network bandwidth, and/or an amount ofdisk space), and/or specialized capabilities available only on a subsetof available computing nodes; constraints related to costs, such asbased on fees or operating costs associated with use of particularcomputing nodes; etc.

As previously noted, in some embodiments, a program execution serviceexecutes third-party customers' programs using multiple physicalcomputing systems (e.g., in one or more data centers) that each hostmultiple virtual machines, with each virtual machine being able toexecute one or more programs for a customer. In some such embodiments,customers may provide programs to be executed to the program executionservice, and may reserve execution time and other resources on physicalor virtual hardware facilities provided by the program executionservice. In addition, customers and/or the program execution service maydefine virtual computer networks that will be used by the programexecution service for computing nodes of the customer, so as totransparently provide computing nodes of a virtual computer network withthe appearance of operating on a dedicated physical network.

In addition, in some situations, a communication manager module maytrack or otherwise determine the virtual computer networks to which themodule's associated computing nodes belong as part of managing thecommunications for the virtual computer networks. The determination by acommunication manager module of a corresponding virtual computer networkfor a computing node may be performed in various ways in variousembodiments, such as by interacting with a system manager module thatprovides that information, by tracking software programs executing onsuch computing nodes, by tracking entities associated with suchcomputing nodes, etc. For example, when a particular computing nodebegins to execute one or more software programs on behalf of a user, andthat user also has other software programs executing on other computingnodes, the new computing node executing the user's program(s) may beselected to be associated with a virtual computer network for the userthat includes those other computing nodes. Alternatively, a user orother entity may specify a particular managed computer network to whicha computing node belongs, such as if the entity maintains multipledistinct managed computer networks between different groups of computingnodes.

Various other types of actions than those discussed with respect toFIGS. 2A-2F may be performed in other embodiments, including for typesof network addressing protocols other than IPv4 and IPv6.

FIG. 3 is a block diagram illustrating example computing systemssuitable for executing an embodiment of a system for managingcommunications between computing nodes. In particular, FIG. 3illustrates a group 399 of computing systems and inter-network(s), suchas a data center or other group of co-located computing nodes. In someembodiments, some or all of the computing systems of the group 399 maybe used by an embodiment of the CNS system to provide managed virtualcomputer networks to users or other entities. The group 399 includes aserver computing system 300, a host computing system 350 capable ofexecuting one or more virtual machines, other host computing systems 390that are similar to host computing system 350, and an optionalCommunication Manager module 360 that manages host computing systems 390and that executes on one of the computing systems 390 or on anothercomputing system (not shown). The server computing system 300 and hostcomputing systems 350 and 390 are connected to one another via aninternal network 380, which includes a physical networking device 362and other networking devices (not shown). The network 380 may be aninter-connection network that joins multiple disparate physical networks(not shown) for the group 399 and possibly provides access to externalnetworks (not shown) and/or systems, such as other computing systems395. In the illustrated example, the networking device 362 provides agateway from the network 380 to the host computing systems 350 and 390.In some embodiments, networking device 362 may, for example, be a routeror a bridge.

The computing system 300 operates to configure and manage virtualcomputer networks within the group 399, as well as to provide otherfunctions (e.g., the provisioning, initialization, and execution ofprograms on computing nodes), including the managing of functionalitycorresponding to virtual peering routers. The computing system 300includes a CPU 305, various I/O components 310, storage 330, and memory320. The I/O components include a display 311, network connection 312,computer-readable media drive 313, and other I/O devices 315 (e.g., amouse, keyboard, speakers, etc.).

The host computing system 350 operates to host one or more virtualmachines, such as for use as computing nodes in managed virtual computernetworks (e.g., computing nodes that execute programs on behalf ofvarious users). The host computing system 350 includes a CPU 352,various I/O components 353, storage 351, and memory 355. While notillustrated here, the I/O components 353 may include similar componentsto those of I/O components 310. A virtual machine Communication Managermodule 356 and one or more virtual machines 358 are executing in thememory 355 (and may each have an associated amount of storage 351 and/orother local computing resources), with the module 356 managingcommunications for the associated virtual machine computing nodes 358.The Communication Manager module 356 maintains various mappinginformation 354 on storage related to the computing nodes 358 and othercomputing nodes, such as in a manner similar to mapping information 212and 262 of FIGS. 2A-2F. The structure of the other host computingsystems 390 may be similar to that of host computing system 350, orinstead some or all of the host computing systems 350 and 390 may actdirectly as computing nodes by executing programs without using hostedvirtual machines. In a typical arrangement, the group 399 may includehundreds or thousands of host computing systems such as thoseillustrated here, organized into a large number of distinct physicalsub-networks and/or networks.

An embodiment of a CNS system 340 is executing in memory 320 of thecomputing system 300. In some embodiments, the system 340 may receive anindication of multiple computing nodes to be used as part of a managedvirtual computer network (e.g., one or more virtual machine computingnodes on host computing system 350 or one or more computing nodes usingone of the host computing systems 390), and in some situations mayselect the particular computing node(s) for the managed virtual computernetwork. In some cases, information about the structure and/ormembership of various managed virtual computer networks may be stored inthe provisioning database 332 on storage 330 by the system 340, such asin a manner similar to information 292 of FIGS. 2A-2D and 2F, andprovided to the Communication Manager modules at various times.Similarly, in some cases, information about the configured networktopology of various managed computer networks (e.g., information aboutlogical subnets, virtual networking devices, intermediate computingnodes along routing paths for communications between particularcomputing nodes, connections to other managed computer networks via oneor more virtual peering routers, etc.) may be stored in the database 334on storage 330 by the system 340, such as in a manner similar toinformation 296 of FIGS. 2C-2F, and provided to the CommunicationManager modules at various times. In this example, the system 340 inmemory 320 includes a Network Routing Manager (“NRM”) module 342 andoptionally other modules 344 (e.g., a system manager module, a paymentmodule to obtain fees from clients if the system manager module does notinclude such payment-related functionality, etc.), with thecommunication manager modules 356 and 360 being a further part of thedistributed CNS system. The NRM module 342 performs operations tofacilitate the configuration and use of specified network topology formanaged computer networks, such as in response to requests from clientsand/or dynamically received routing information, as discussed elsewhere.In at least some embodiments, the NRM module 342, other modules 344,and/or various communication manager modules may each include softwareinstructions that may be stored on long-term non-volatile storage (e.g.,storage 330, storage 351, etc.) and may be loaded into memory (e.g.,memory 320, memory 355, etc.) for execution by at least one of one ormore processors (e.g., CPU 305, CPU 352, etc.), so as to program orotherwise configure those processors and the corresponding computingsystems/devices to perform the described techniques.

As discussed in greater detail elsewhere, the Communication Managermodules 356 and 360 (and other Communication Manager modules, not shown,that manage other associated computing nodes, not shown) and the variousmodules 342 and 344 of the system 340 may interact in various ways tomanage communications between computing nodes, including to providevirtual networking functionality corresponding to configured networktopologies for provided virtual computer networks, including withrespect to virtual peering routers. Such interactions may, for example,enable the computing nodes 358 and/or other computing nodes tointer-communicate over managed virtual computer networks without anyspecial configuration of the computing nodes, by overlaying the virtualcomputer networks over network 380 and optionally one or more externalnetworks (not shown) without any special configuration of networkingdevice 362 or other networking devices (not shown), and optionallywithout encapsulation of communications.

It will be appreciated that computing systems 300, 350, 390, and 395,and networking device 362, are merely illustrative and are not intendedto limit the scope of the present invention. For example, computingsystems 300 and/or 350 may be connected to other devices that are notillustrated, including through one or more networks external to thegroup 399, such as the Internet or via the World Wide Web (“Web”). Moregenerally, a computing node or other computing system may comprise anycombination of hardware or software that can interact and perform thedescribed types of functionality, including without limitation desktopor other computers, database servers, network storage devices and othernetwork devices, PDAs, cell phones, wireless phones, pagers, electronicorganizers, Internet appliances, television-based systems (e.g., usingset-top boxes and/or personal/digital video recorders), and variousother consumer products that include appropriate communicationcapabilities. In addition, the functionality provided by the illustratedmodules may in some embodiments be combined in fewer modules ordistributed in additional modules, such as if the functionality of asystem manager module and a network routing manager module are insteadcombined into a single module. Similarly, in some embodiments thefunctionality of some of the illustrated modules may not be providedand/or other additional functionality may be available. Furthermore, insome embodiments the functionality of a single illustrated module may bedistributed across multiple related modules that provide the describedfunctionality in an aggregate manner.

It will also be appreciated that, while various items are illustrated asbeing stored in memory or on storage while being used, these items orportions of them may be transferred between memory and other storagedevices for purposes of memory management and data integrity.Alternatively, in other embodiments some or all of the modules and/orsystems may execute in memory on another device and communicate with theillustrated computing systems via inter-computer communication.Furthermore, in some embodiments, some or all of the systems and/ormodules may be implemented or provided in other manners, such as atleast partially in firmware and/or hardware, including, but not limitedto, one or more application-specific integrated circuits (ASICs),standard integrated circuits, controllers (e.g., by executingappropriate instructions, and including microcontrollers and/or embeddedcontrollers), field-programmable gate arrays (FPGAs), complexprogrammable logic devices (CPLDs), etc. Some or all of the modules,systems and data structures may also be stored (e.g., as softwareinstructions or structured data) on a computer-readable medium, such asa hard disk, a memory, a network, or a portable media article to be readby an appropriate drive or via an appropriate connection. The systems,modules and data structures may also be transmitted as generated datasignals (e.g., as part of a carrier wave or other analog or digitalpropagated signal) on a variety of computer-readable transmissionmediums, including wireless-based and wired/cable-based mediums, and maytake a variety of forms (e.g., as part of a single or multiplexed analogsignal, or as multiple discrete digital packets or frames). Suchcomputer program products may also take other forms in otherembodiments. Accordingly, the present invention may be practiced withother computer system configurations.

FIG. 4 is a flowchart of an example embodiment of a CNS System Managerroutine 400. The routine may be provided by, for example, execution ofthe system manager module 110 of FIG. 1B, the manager module 110 of FIG.1A, the system manager module 290 of FIGS. 2A-2F, and/or a systemmanager module (not shown) of CNS system 340 of FIG. 3, such as toassist in managing communications between multiple computing nodesacross one or more intermediate networks, including to managecommunications so as to provide virtual networking functionalitycorresponding to configured network topologies of managed computernetworks, including based on connections to virtual peering routers, aswell as to perform other types of management operations in somesituations. In at least some embodiments, the routine may be provided aspart of a system that manages communications for multiple differententities across a common intermediate network, with the communicationsconfigured so as to enable each computing node to transparentlycommunicate with other associated computing nodes using a privatevirtual computer network that is specific to that entity. Furthermore,the routine may facilitate preventing unauthorized communications frombeing provided to destination computing nodes, such as by assistingCommunication Manager modules with determinations of whethercommunications are authorized.

In the illustrated embodiment, the routine begins at block 405, where arequest is received. The routine continues to block 410 to determine thetype of request. If it is determined that the type of request is toassociate one or more computing nodes with a particular managed virtualcomputer network provided for an indicated entity, such as if thosecomputing nodes are executing or are to execute one or more programs onbehalf of that entity, the routine continues to block 415 to associatethose computing nodes with that indicated entity and virtual computernetwork. In some embodiments, the routine may further determine the oneor more computing nodes to be associated with the indicated entity andvirtual computer network, such as based on information provided by theindicated entity, while in other embodiments the selection of suchcomputing nodes and/or execution of appropriate programs on thosecomputing nodes may be performed in other ways. In addition, asdiscussed in greater detail elsewhere, in some embodiments one or moreof the computing nodes may each be a virtual machine that is hosted byone or more physical computing systems. The routine then continues toblock 420 to store mapping information for the computing nodes and themanaged virtual computer network. In particular, in the illustratedembodiment the routine stores for each computing node an indication of aphysical substrate network address corresponding to the computing node,a virtual network address used by the entity for the computing node aspart of the virtual computer network, optionally a virtual hardwareaddress assigned to the computing node, and an indication of theassociated entity. As discussed in greater detail elsewhere, thephysical substrate network address corresponding to the computing nodemay in some embodiments be a substrate network address specific to thatsingle computing node, while in other embodiments may instead refer to asub-network or other group of multiple computing nodes, such as may bemanaged by an associated Communication Manager module. In addition, thespecification of various network topology information for computingnodes and virtual networking devices is discussed in greater detail withrespect to block 480 and FIGS. 6A-6B, such as to be further included inthe stored mapping information as discussed in greater detailpreviously, although in other embodiments such information could furtherbe received and stored with respect to block 420. After block 420, theroutine continues to block 422 to optionally provide information aboutthe computing nodes and their configuration to one or more communicationmanager modules associated with those computing nodes, although in otherembodiments instead provides such information upon request from thecommunication manager modules.

If it is instead determined in block 410 that the type of receivedrequest is a request for address resolution for a virtual networkaddress of a target computing node or other network device of interest,such as from a communication manager module on behalf of a managedcomputing node, the routine continues instead to block 425, where itdetermines whether the request is authorized in one or more ways, suchas based on whether the managed computing node on whose behalf therequest is made is authorized to send communications to a computing nodewhose virtual network address resolution is requested (e.g., based onthe virtual computer network(s) to which the two computing nodes belong,and optionally any inter-connections between multiple such virtualcomputer networks via one or more virtual peering routers), based onwhether the managed computing node on whose behalf the request is madeis a valid computing node that is currently part of a configured virtualcomputer network, and/or based on whether the request is received fromthe communication manager module that actually manages the indicatedcomputing node on whose behalf the request is made. If the request isdetermined to be authorized, the routine continues to block 430, whereit obtains a virtual network address of interest for a particularvirtual computer network, such as may be included with the requestreceived in block 405, or previously stored and currently identifiablefor the target computing node of interest based on other receivedinformation. The routine then continues to block 435 to retrieve storedinformation for the computing node that is associated with the virtualnetwork address for the virtual computer network, and in particularinformation that associates that virtual network address to a physicalsubstrate network address for a network location that corresponds to thecomputing node, such as may be previously stored with respect to block420, and optionally to other information for the virtual network address(e.g., an associated virtual hardware address, an indication regardingwhether the virtual network address corresponds to a physicallyimplemented computing node with an actual substrate network address orinstead to a virtual networking device that does not have an actualsubstrate network address, information about a role or status of thedevice corresponding to the virtual network address with respect toconfigured network topology information, information about whether thevirtual network address corresponds to a distinct remote managedcomputer network that is reachable via connections ton one or morevirtual peering routers, etc.). Furthermore, in situations in which thedestination virtual network address corresponds to a distinct remotemanaged computer network that is accessible via a virtual peeringrouter, and the virtual peering router is configured to provide NATfunctionality with respect to communications between the two managedcomputer networks, the routine may further translate between theindicated virtual network address and a distinct actual virtual networkaddress that is used for the destination computing node by thedestination managed computer network. If communications from thecomputing node on whose behalf the request is made to the indicatedcomputing node are to be routed via one or more intermediate computingnodes, the information that is provided may in part correspond to afirst of those intermediate computing nodes, such as to include theactual substrate network address of that first intermediate computingnode (whether instead of or in addition to the actual substrate networkaddress for the indicated computing node). After block 435, the routinecontinues to 440 to provide an indication of the retrieved informationto the requester. While not illustrated here, if the determination inblock 425 determines that the request is not authorized, the routine mayinstead not perform blocks 430-440 for that request, such as byresponding with an error message to the request received in block 405 ornot responding to that received request. In addition, in otherembodiments the routine may perform one or more other tests to validatea received request before responding with the requested information,such as to verify that the computing node that initiated the request isauthorized to receive that information.

If it is instead determined in block 410 that the received request is toconfigure information regarding a specified network topology for anindicated managed virtual computer network and/or inter-connectionsbetween two or more managed virtual computer networks via one or morevirtual peering routers, such as from a user associated with thatvirtual computer network (e.g., a user representative of the client onwhose behalf the virtual computer network is provided), the routinecontinues to block 480 to perform a Network Routing Manager routine tomanage the configuration. One example embodiment of such a NetworkRouting Manager routine is described in further detail with respect toFIGS. 6A-6B. In this illustrated embodiment, the Network Routing Managerroutine manages the interaction with the user to obtain the configurednetwork topology information (e.g., via an API and/or GUI of theconfigurable network service), and stores relevant configured networktopology information in a manner that is accessible by the SystemManager routine for later use (e.g., with respect to block 435), whilein other embodiments the System Manager routine may instead manage thoseuser interactions and/or that network topology information storage(e.g., by providing received configured network topology information tothe Network Routing Manager routine for analysis after it is received bythe System Manager routine, and by storing updated network topologyinformation if it is received from the Network Routing Manager routine).

If it is instead determined in block 410 that the received request is ofanother type, the routine continues instead to block 490 to performanother indicated operation as appropriate. For example, in someembodiments, the routine may receive requests to update storedinformation about particular computing nodes, such as if a particularcomputing node was previously associated with a particular entity and/orvirtual computer network (or portion of a virtual computer network, suchas a specified logical subnet) but that association ends (e.g., one ormore programs being executed for that entity on that computing node areterminated, the computing node fails or otherwise becomes unavailable,an associated user or other client changes specified configurationinformation for the computing node, etc.). The routine may also performa variety of other actions related to managing a system of multiplecomputing nodes (e.g., charging fees to clients for particularfunctionality provided to those clients, obtaining payment from clientsfor such charged fees, etc.), as discussed in greater detail elsewhere,and may at times perform actions of other types, such as to performoccasional housekeeping operations to review and update storedinformation as appropriate (e.g., after predefined periods of time haveexpired). In addition, if possible validation problems are detected,such as with respect to received address resolution requests for virtualnetwork addresses, the routine may take various actions to signal anerror and/or perform other corresponding actions as appropriate.Furthermore, if the routine receives updated network topologyinformation for a managed virtual computer network, such as from theclient and/or from the Network Routing Manager module, the routine mayproceed to store that information for later use as appropriate.

After blocks 422, 440, 480 or 490, the routine continues to block 495 todetermine whether to continue, such as until an explicit indication toterminate is received. If it is determined to continue, the routinereturns to block 405, and if not continues to block 499 and ends.

FIGS. 5A-5B are a flow diagram of an example embodiment of a CNSCommunication Manager routine 500. The routine may be provided by, forexample, execution of the Communication Manager modules 109 a-109 d, 108and/or 150 of FIG. 1B, the Communication Manager modules 210 and/or 260of FIGS. 2A-2F, the Communication Manager modules 356 and/or 360 of FIG.3, and/or a communication manager module (not shown) of the CNS service105 of FIG. 1A, such as to manage communications to and from anassociated group of one or more computing nodes in order to provide aprivate virtual computer network over one or more shared intermediatenetworks, including to determine whether to authorize communications toand/or from the managed computing nodes, and to support providingvirtual networking functionality corresponding to configured networktopologies for managed virtual computer networks.

The routine begins at block 505, where an indication is received of anode communication or other message. The routine continues to block 510to determine the type of communication or other message and proceedaccordingly. If it is determined in block 510 that the message is arequest from an associated managed computing node for network addressresolution, such as an ARP request, the routine continues to block 515to identify the virtual network address of interest indicated in therequest. The routine then continues to block 520 to send a request to asystem manager module for virtual network address resolution for theindicated virtual network address for the virtual computer network thatis associated with the computing node that provided the request, such asdiscussed with respect to blocks 425-440 of FIG. 4. As discussed ingreater detail elsewhere, the routine may in some embodiments trackinformation about virtual computer networks and/or entities associatedwith each managed computing node, while in other embodiments at leastsome such information may instead be provided to the routine by thecomputing nodes, by the system manager module and/or by the networkrouting manager module, or instead the system manager module may trackand store that information without it being provided to and tracked bythe current routine. While not illustrated here, in other embodimentsand situations such address resolution requests may be handled in othermanners. For example, if a computing node being managed by a particularcommunication manager module provides an address resolution request foranother computing node that is also managed by that communicationmanager module, the routine may instead respond to the request withoutinteraction with the system manager module, such as based on locallystored information. In addition, while in the illustrated embodiment thereceived request is a request to provide a computing node's link-layerhardware address that corresponds to an indicated networking layeraddress, in other embodiments the address resolution request may haveother forms, or computing nodes may request other types of informationabout indicated computing nodes.

In the illustrated embodiment, the routine next continues to block 525to receive a response from the system manager module that includes aphysical substrate network address and/or other informationcorresponding to the identified virtual network address, and storesinformation locally that maps that physical substrate network addressand/or other information to a unique hardware address for later use bythe routine (e.g., based on a dummy virtual hardware address generatedby the routine or provided in the response), along with otherinformation about the computing node as discussed in greater detailelsewhere. The routine then provides the hardware address to therequesting computing node, which it may use as part of one or more latercommunications that it sends to the computing node with the indicatedvirtual network address. As discussed in greater detail elsewhere, thephysical substrate network address response that is provided may in someembodiments include a physical substrate network address that isspecific to the indicated computing node of interest, while in otherembodiments the physical substrate network address may correspond toanother intermediate computing node via which communications to theindicated computing node of interest will be passed for some or allsending computing nodes, or may instead correspond to a sub-network orother group of multiple computing nodes to which the indicated computingnode belongs, such as to correspond to another communication managermodule that manages those other computing nodes. If only some inter-nodecommunications to an indicated computing node of interest will be passedthrough a particular intermediate computing node, such as for only somesending computing nodes, it will be appreciated that the routine mayobtain and store multiple entries for the indicated computing node ofinterest, such as to include different information to use for differentsending computing nodes that initiate inter-node communications to theindicated computing node of interest. The routine next continues toblock 530 to determine if blocks 515-525 were performed as part of thehandling of an outgoing node communication, as discussed with respect toblocks 540-560, and if so, continues to block 547, or otherwisecontinues to block 595. While not illustrated here, in some embodimentsthe routine may instead receive an error response from the systemmanager module (e.g., based on the requesting computing node not beingauthorized to communicate with the indicated destination computing node)or no response, and if so may not send any response or a correspondingerror message to the requesting computing node.

If it is instead determined in block 510 that the type of communicationor other message is an outgoing communication from a computing nodemanaged by the routine, such to another indicated remote destinationcomputing node that is not managed by the routine and/or to an indicatedvirtual networking device, the routine continues to block 540. If theroutine is being performed for a communication manager module thatoperates as an edge module to manage connections between a group ofcomputing nodes connected by a substrate network (e.g., at a datacenter) and external computing systems, such outgoing communicationscorrespond to communications entering the group of inter-connectedcomputing nodes from external computing systems, and the routineproceeds to block 547 without performing blocks 540-545. In block 540,the routine identifies the indicated hardware address for thedestination from the communication header for the outgoingcommunication. In block 545, the routine then determines whether thatdestination hardware address is a hardware address previously mapped toa physical substrate network address corresponding to the destination,such as previously discussed with respect to block 525. If not, in someembodiments the routine continues to block 515 to perform blocks 515-525to determine such a corresponding physical network address for theoutgoing node communication, while in other embodiments such actions arenot performed (e.g., if the indicated hardware address is not a mappedaddress, the routine may cause the outgoing node communication to fail,such as with an error message back to the sending node).

If the indicated hardware address is a mapped address, or the check isnot performed, the routine continues to block 547 to determine if thereceived communication is a routing-related communication, such as acommunication intended for a virtual networking device or for a virtualpeering router. If so, the routine continues to block 581, and otherwisecontinues to block 550 to retrieve the physical substrate networkaddress that is mapped to the hardware address for the destinationcomputing node to which the communication is directed (or to thedestination network address for incoming communications from externalcomputing systems). As discussed in greater detail elsewhere, if thecommunication is to be directed to one or more intermediate computingnodes along a routing path to the final destination computing node, thesubstrate network address that is used may correspond to a first suchintermediate computing node as an initial destination. In addition, ifthe communication is sent from a first computing node of a first managedcomputer network and is directed to a second computing node of adistinct second managed computer network, and the first computing nodeis authorized to send the communication to the second computing node(e.g., based on the first and second managed computer networks eachbeing connected to one or more inter-connected virtual peering routers,and based on corresponding peering configuration information specifiedfor those one or more virtual peering routers), the substrate networkaddress that is used corresponds to the second computing node, despitethe second computing node being part of a different virtual computernetwork. After block 550, the routine in block 555 then rewrites thecommunication header in accordance with a networking address protocolfor one or more intermediate networks between the communication managermodule and the destination computing node using the physical substratenetwork address retrieved in block 550. The header re-writing mayfurther include changing other information in the new header, includingchanging a virtual network address for the sending computing node to bea corresponding physical substrate network address so as to directresponses to a communication manager module associated with the sendingcomputing node (e.g., to an edge communication manager module for anexternal computing system that sent the communication), and in at leastsome embodiments includes modifying the received communication withoutencapsulation as part of an overlay of the virtual computer network overthe substrate one or more intermediate physical networks. Furthermore,for a communication whose destination hardware address does correspondto a virtual networking device, the routine in block 555 may furtherperform other modifications that correspond to providing virtualnetworking functionality to emulate the actions and functionality thatwould be performed by the one or more virtual networking devices thatwould be used to forward the communication to the destination computingnode in accordance with the configured network topology for the virtualcomputer network. Similarly, for a communication that is directed to acomputing node of a different managed computer network via one or moreintermediate virtual peering routers, the routine in block 555 mayfurther perform other modifications that correspond to providing virtualnetworking functionality to emulate the actions and functionality thatwould be performed by the one or more virtual peering routers that wouldbe used to forward the communication to the destination computing nodein accordance with the configured network topology for the virtualcomputer network. Moreover, in situations in which the one or more suchvirtual peering routers are configured to provide NAT functionality, therewriting of the header may further include replacing the indicatedvirtual network address for the destination computing node with adistinct actual virtual network address for the destination computingnode that is used by the destination managed computer network, althoughin other embodiments such NAT functionality may instead be performed inother manners (e.g., by a distinct communication manager module thatreceives the forwarded communication on behalf of the destinationcomputing node).

In block 560, the routine then facilitates providing of the modifiedoutgoing communication along the routing path to the destinationcomputing node, such as by initiating forwarding of the modifiedoutgoing communication over the substrate intermediate network(s) to thedestination computing node. While not illustrated here, in otherembodiments various additional types of processing may be performed foroutgoing node communications, such as to verify that the communicationsare valid or otherwise authorized in various ways (e.g., to verify thatthe sending computing node is authorized to send communications to thedestination computing node, such as based on being associated with thesame entity or part of the same virtual computer network, based on thesending and destination computing nodes being associated with differententities that are authorized to inter-communicate, based on the sendingand destination computing nodes being part of distinct managed computernetworks that are inter-connected via one or more virtual peeringrouters, based on the type of communication or other informationspecific to the communication, etc.), to add and/or remove a VLANidentifier or other information about a VLAN configured for the networktopology and associated with the communication (e.g., based on the typeof VLAN communication links associated with the sending and destinationcomputing nodes, such as if the communication manager module for anoutgoing communication performs such a modification rather than thecommunication manager module for an incoming communication), etc.

If it is instead determined in block 547 that the received communicationis a routing-related communication intended for a virtual peering routeror other virtual networking device, the routine continues instead toblock 581 to forward the received routing-related communication to theNetwork Routing Manager routine for analysis, as discussed in greaterdetail with respect to FIGS. 6A-6B. The communication may be forwardedto the Network Routing Manager routine in various manners, including byre-headering the communication and forwarding it over the intermediatesubstrate network to a location of the Network Routing Manager modulethat performs the Network Routing Manager routine, in a manner similarto that discussed in greater detail elsewhere. In other embodiments, theroutine may instead extract particular routing information from thecommunication and instead forward the extracted routing information tothe Network Routing Manager routine as part of such a communication orinstead in another manner (e.g., via a defined API of the NetworkRouting Manager). After block 581, the routine continues to block 583 tooptionally generate a response communication to the computing node orexternal device from which the routing-related communication wasreceived (e.g., to acknowledge receipt), such as if the predefinedrouting protocol in use includes such response communications, andforwards the generated response communication to that sender computingnode or external device. After block 583, the routine continues to block595.

If it is instead determined in block 510 that the received message is anincoming node communication for one of the managed computing nodes, suchas an inter-node communication from an external computing node that isnot managed by the communication manager module and/or a routing-relatedcommunication from the Network Routing Manager routine (e.g., arouting-related communication that is spoofed to include senderinformation corresponding to a virtual peering router or other virtualnetworking device), the routine continues to block 565. If the routineis being performed for a communication manager module that operates asan edge module to manage connections between a group of computing nodesconnected by a substrate network (e.g., at a data center) and externalcomputing systems, such incoming communications correspond tocommunications exiting the group of inter-connected computing nodes toexternal computing systems. In block 565, the routine identifies thephysical substrate network addresses for the sender and for thedestination computing node from the communication header. After block565, the routine continues to block 570 to optionally verify that theincoming communication is valid in one or more ways. For example, theroutine may determine whether the physical substrate network address forthe sender is actually mapped to a sending computing node thatcorresponds to the source physical substrate network address location,such as based on interactions with a system manager module and/or basedon other information previously obtained and stored by the routine. Inaddition, the routine may determine whether the physical substratenetwork address for the destination computing node corresponds to anactual managed computing node, or to an external computing system ordevice with which communications are authorized. While not illustratedhere, if an incoming communication is determined to not be valid, theroutine may take various actions not shown, such as to generate one ormore errors and perform associated processing and/or drop the incomingcommunication without forwarding it to the indicated destination node.For example, if the incoming communication indicates a destinationnetwork address that does not correspond to a current managed computingnode or authorized external device, the routine may drop the incomingcommunication and/or initiate an error message, although in someembodiments such error messages are not sent to the sending computingnode.

In the illustrated embodiment, after block 570, the routine continues toblock 575 to retrieve the hardware address and the network address thatare mapped to the physical destination substrate network address, and torewrite the communication header in a manner corresponding to thevirtual computer network, so that it includes information directed tothe destination computing node. For example, in some embodiments thedestination network address may be obtained from the destinationphysical substrate network address itself, such as from a subset of thebits of the destination physical substrate network address, while inother embodiments the destination network address may be indicated inother manners (e.g., stored in one or more header fields of thecommunication). In addition, the destination hardware address may havepreviously been mapped to information about the location of thedestination computing node, such as previously discussed with respect toblock 525. In situations in which such prior mapping has not occurred,the routine may instead perform blocks 515-525 to obtain suchinformation, although those actions are not illustrated here. Theroutine may similarly rewrite the communication header for the virtualcomputer network so that it appears to be sent from a sender with asource virtual network address and source hardware address correspondingto the sender. In addition, in at least some embodiments, the routine inblock 575 may further perform other modifications to the incomingcommunication that correspond to providing virtual networkingfunctionality to emulate the actions and functionality that would beperformed if the communication was forwarded in a manner associated witha configured VLAN for the managed virtual computer network, such as toadd and/or remove a VLAN identifier or other VLAN information, althoughin other embodiments such a modification is not performed for anincoming communication if it was instead performed for the communicationwhen outgoing for another communication manager module, or if nomodification is needed based on the configured VLAN communication linksassociated with the sending and destination computing nodes.Furthermore, in at least some embodiments, the routine in block 575 mayfurther perform other modifications to the incoming communication thatcorrespond to providing virtual networking functionality to emulate theactions and functionality that would be performed by one or more virtualpeering routers and/or other virtual networking devices that would havebeen used to forward the communication to the destination computing nodein accordance with the configured network topology for the virtualcomputer network. Moreover, in situations in which the communication wasreceived from a computing node in another managed virtual computernetwork that is connected to the destination computing node's managedvirtual computer network via one or more virtual peering routers, and inwhich one or more virtual peering routers are configured to provide NATfunctionality, the rewriting of the header may further include replacingan initially indicated virtual network address for the destinationcomputing node with a distinct actual virtual network address for thedestination computing node that is used by the destination managedcomputer network, although in other embodiments such NAT functionalitymay instead be performed in other manners (e.g., by a distinctcommunication manager module that forwarded the communication on behalfof the sending computing node). After block 575, the routine continuesto block 580 to facilitate providing of the modified incomingcommunication to the destination computing node, such as by initiatingforwarding of the modified incoming communication to the destinationnode. While the incoming communication may be a routing communicationthat is directed to a managed computing node of the communicationmanager module by the Network Routing Manager, such routingcommunications may in other embodiments instead be generated by thecommunication manager module that manages that computing node (e.g., asinstructed by the Network Routing Manager, and such as to includerouting information supplied by the Network Routing Manager), andprovided to the destination computing node.

If it is instead determined in block 510 that a message of another typeis received, the routine continues to block 590 to perform anotherindicated operation as appropriate, such as to store information aboutentities associated with particular computing nodes, store informationabout configured network topologies for particular virtual computernetworks (including connections to any virtual peering routers), respondto requests and other messages from computing nodes in a manner toprovide virtual networking functionality corresponding to configurednetwork topologies for virtual computer networks (e.g., by emulatingactions and other functionalities that would be performed by specifiedvirtual networking devices if they were physically implemented), updatepreviously mapped or stored information to reflect changes with respectto computing nodes that are being managed or to remote computing nodes,etc. The storing and/or updating of stored information may be initiatedin various manners, such as by receiving information in response toprevious requests, receiving information that is proactively pushed tothe routine without a corresponding request, etc. In addition, inembodiments in which clients pay fees for various types of functionalityprovided to them, such as usage-based fees, the routine may furthertrack corresponding usage and provide such information to the systemmanager module (e.g., periodically, as soon as usage occurs, etc.).

After blocks 560, 580, 583, or 590, or if it is instead determined inblock 530 that the processing is not being performed with respect to anoutgoing communication, the routine continues to block 595 to determinewhether to continue, such as until an explicit indication to terminateis received. If it is determined to continue, the routine returns toblock 505, and if not continues to block 599 and ends.

FIGS. 6A-6B are a flow diagram of an example embodiment of a CNS NetworkRouting Manager routine 600. The routine may be provided by, forexample, execution of the NRM module 342 of FIG. 3, the NRM module 295of FIGS. 2E and 2F, the Network Routing Manager module 170 of FIG. 1B, aNetwork Routing Manager module (not shown) of the CNS service 105 ofFIG. 1A, and/or a Network Routing manager module (not shown) thatoperates in conjunction with the System Manager module 290 of FIGS.2A-2D and/or to support the virtual computer networks 175 of FIG. 1C,such as to manage the configuration of specified network topologyinformation for managed computer networks, including inter-connectionsbetween managed computer networks via one or more virtual peeringrouters. In the illustrated embodiment, the routine may be invoked by,for example, execution of block 480 of FIG. 4 and/or directly inresponse to a request initiated by a client of the CNS system, and mayreceive information forwarded by block 581 of FIGS. 5A-5B. In addition,in the illustrated embodiment of the routine, a Network Routing managermodule facilitates the configuration of specified network topologyinformation for managed virtual computer networks, and providescorresponding information to a system manager module that furtherinteracts with communication manager modules based on the specifiednetwork topology information—in other embodiments, however, variousfunctionality may be distributed in other manners, such as to combinesome or all functionality of a Network Routing manager module, a systemmanager module, and/or one or more communication manager modules.

The routine begins at block 605, where an indication is received ofinformation related to the configuration of a managed computer network.The routine continues to block 610 to determine whether the indicationis related to the initial configuration of network topology informationfor a managed virtual computer network, such as part of initiallycreating the managed virtual computer network. If so, the routinecontinues to block 615 to obtain various information about theconfigured network topology, such as information previously received inblock 605, or by interacting with a user or other entity for a clientproviding the configuration information. The obtained information mayinclude, for example, information regarding logical subnets of themanaged computer network and optionally corresponding computing nodesand/or virtual networking devices, information about any computing nodesthat are configured to act as intermediate computing nodes for at leastsome inter-node communications for at least some computing nodes,information about any special-purpose handling of at least someinter-node communications for at least some computing nodes, etc.

The routine next continues to blocks 620-635 to analyze the receivedconfiguration information to determine particular information to use inrouting communications between computing nodes. In particular, in block620, the routine selects the next computing node of the managed computernetwork, beginning with the first. In block 625, the routine then, foreach other computing node of the managed computer network, determines ifinter-node communications from the selected computing node to the othercomputing node are configured to pass through one or more intermediatecomputing nodes based on the configured network topology. If so, theroutine selects the substrate network address for a first suchintermediate computing node to use for communications directed from theselected computing node to the other computing node, and otherwiseselects the substrate network address for the other computing node touse for such inter-node communications. In block 630, the routine thenstores such received information (e.g., in a manner accessible to asystem manager module, such as by providing the received information tothe system manager module), and optionally provides the configurationinformation (e.g., in a push manner) to one or more communicationmanager modules, including the communication manager module that managesthe selected computing node. In block 635, the routine then determinesif there are more computing nodes to analyze, and if so returns to block620, and otherwise continues to block 695. While illustrated here asperforming the analysis in a serial manner for individual computingnodes, in other embodiments and situations such analysis may beperformed in other manners.

If it is instead determined in block 610 that the received indication isrelated to a possible update of network topology information for amanaged virtual computer network, such as based on a routing-relatedcommunication received via a communication manager module and/or basedon an update to network topology information specified by the associatedclient, the routine continues to block 645. In block 645, the routinedetermines whether routing information has been received in a routingcommunication for a managed computer network, and if so continues toblock 650 to extract the routing information from the communication andoptionally store it for later use (e.g., as discussed with respect toblock 690). After block 650, the routine continues to block 652 todetermine whether the routing communication was directed to a virtualpeering router from the managed computer network. If so, the routinecontinues to block 654, and otherwise continues to block 657 to handlethe routing communication sent within the managed computer network. Inblock 657, the routine determines if there are any computing nodes ofthe managed computer network to update with the received routinginformation, such as based on the configured network topology of themanaged computer network. In particular, if the received routinginformation was directed to a particular virtual networking device ofthe managed computer network, the routine may identify other computingnodes of the managed computer network to which that networking devicewould forward routing information if that networking device werephysically provided, such as based on the network topology of themanaged computer network. For example, if the routing-relatedcommunication was sent by a first computing node of the managed computernetwork that participates in one or more routing-related protocols, andwas directed to a specified virtual networking device of the managedcomputer network that connects the first computing node to one or moreother second computing nodes of the managed computer network that alsoparticipate in one or more routing-related protocols for the managedcomputer network, the routine may select at least one (e.g., all) of thesecond computing nodes to receive corresponding routing information. Theroutine may determine such computing nodes of the managed computernetwork that participate in one or more routing protocols for themanaged computer network in various manners, such as based onconfiguration information supplied by a client for whom the managedcomputer network is provided, and/or based on tracking which computingnodes issue routing-related communications.

If the routine instead continues to block 654 to handle a routingcommunication directed to a virtual peering router from a managedcomputer network, the routine in block 654 analyzes the routinginformation in the routing communication, as well as any peeringconfiguration information previously specified for the managed computernetwork and for any other managed computer networks connected to thevirtual peering router (whether directly connected to that virtualpeering router, or indirectly via one or more other virtual peeringrouters that are connected to that virtual peering router). As part ofthe analysis, the routine identifies any other managed computer networksthat are connected to the virtual peering router to which the receivedrouting information should be forwarded, and determines particularcomputing nodes of those identified managed computer network(s) toupdate with the received routing information.

After blocks 654 or 657, the routine then continues to block 659 toprovide routing information that corresponds to the routing informationobtained in block 650 to the computing nodes determined in block 654 or657, such as by sending a routing communication with such correspondingrouting information to each of the determined computing nodes. If therouting information obtained in block 650 was directed to a particularvirtual networking device of the managed computer network, the routinemay determine particular routing information that the particular virtualnetworking device would forward on if that networking device werephysically provided, such as in a manner relative to a position of thatvirtual networking device based on the network topology of the managedcomputer network. For example, if the virtual networking device isconfigured to select shortest paths to destinations by usingdistance-based cost information, the routine may use its availableinformation for the entire managed computer network to determine thevarious shortest paths from the location of the virtual networkingdevice to the various possible destinations, including based on therouting information received in block 650. Alternatively, if the routinginformation obtained in block 650 was directed to a particular virtualpeering router, the routine may determine particular routing informationthat the virtual peering router would forward on if that peering routerwere physically provided, such as in a manner relative to connections ofthat virtual peering router to virtual networking devices and/orcomputing nodes of managed computer networks that are connected to thatvirtual peering router. It will be appreciated that the routine mayoperate in other manners in other embodiments, such as by determiningbest path information in manners other than using distance-based costinformation, by determining best path information for a particularvirtual networking device in a localized manner for that virtualnetworking device rather than using globally available information forthe entire managed virtual computer network, etc. In addition, it willbe appreciated that peering configuration information may be specifiedin various manners, including by indicating policies at varying degreesof specificity and abstractness, and may be analyzed in various mannersto determine how to handle routing communications and computing nodecommunications directed to the virtual peering router.

If it is instead determined in block 645 that the network topologyinformation is received from the client, the routine continues to block655 to update the stored network topology information for the managedvirtual computer network in accordance with the received information.After block 655, the routine continues to block 657 and 659 to determinewhether to send any routing information to any computing nodes of themanaged computer network, as discussed above. After block 659, theroutine continues to block 660 to determine if the updates correspondingto the received information affect the routing paths for any inter-nodecommunications, such as in a manner similar to that previously discussedwith respect to blocks 620-635.

After block 660, the routine continues to block 665 to determine if theindication received in block 605 is an indication to connect anindicated managed virtual computer network to a virtual peering router,such as from the client to whom that managed virtual computer network isprovided. If not, the routine continues to block 685, but otherwisecontinues to block 667 to update the network topology information forthe indicated managed computer network to reflect the connection to thevirtual peering router. A received indication to connect an indicatedmanaged virtual computer network to a virtual peering router may bespecified in various manners (e.g., by a client associated with themanaged virtual computer network, such as via a GUI or API provided bythe configurable network service; by the managed virtual computernetwork, such as based on a communication or other message that isdirected to the virtual peering router or that otherwise indicates arequest to communicate with the virtual peering router; etc.), and mayin some embodiments and situations include various peering configurationinformation for the indicated managed virtual computer network.Depending on the existing configuration (if any) of the virtual peeringrouter, including any other managed computer networks that are alreadyconnected to the virtual peering router, the update of the networktopology information for the indicated managed computer network mayinclude an indication that some or all of the computing nodes of one ormore such other managed computer networks are now accessible to theindicated managed computer network. In addition, if the indication inblock 605 is further to create or otherwise provide a new virtualpeering router to which the indicated managed computer network is to beconnected, the routine in block 667 may further perform variousoperations to create that virtual peering router, including to store anypeering configuration information specified by the client for thevirtual peering router (e.g., information regarding how/when/whetherother managed computer networks may connect to the virtual peeringrouter and/or may send or receive communications via the virtual peeringrouter). After block 667, the routine continues to block 670 to updatenetwork topology information for any other managed computer networksthat were previously connected to the virtual peering router, in orderto reflect the new connection of the indicated managed computer networkto the virtual peering router. In a manner similar to that for the newlyconnected indicated managed computer network, and depending on theexisting peering configuration (if any) of the virtual peering routerand/or new peering configuration (if any) by the client for theindicated managed computer network of the virtual peering router, theupdate of the network topology information for the other managedcomputer networks may include an indication that some or all of thecomputing nodes of the indicated managed computer network are nowaccessible to one or more of the other managed computer networks. Whilenot illustrated in blocks 667-670, the routine may in some embodimentstake further actions when a request to connect an indicated managedcomputer network to an indicated virtual peering router is received,including to determine whether the establishment of that new connectionis authorized. Such a determination of authorization may be made invarious manners (e.g., based on previously specified peeringconfiguration for the virtual peering router, such as from a creator ofthe virtual peering router and/or from one or more other managedcomputer networks that are already connected to the virtual peeringrouter and/or from the configurable network service; based on queryingthe other managed computer networks that are already connected to thevirtual peering router or the clients to whom those other managedcomputer networks are provided, or otherwise receiving an indicationthat those other managed computer networks do not reject the newconnection; etc.), and if a connection request is determined not to beauthorized, the routine continues instead to block 685 withoutperforming blocks 667-670. In addition, as part of performing blocks 667and/or 670, the routine may in some embodiments determine to send one ormore routing communications to the newly connected managed computernetwork and/or to one or more previously connected managed computernetworks (e.g., to provide information about other connected managedcomputer networks, such as in accordance with peering configurationinformation specified for the virtual peering router), such as in amanner similar to that previously discussed with respect to blocks 654,657 and 659, while in other embodiments the routine will instead waituntil routing communications directed to the virtual peering router arereceived from connected managed computer networks, and handle suchreceived routing communications accordingly (as discussed with respectto blocks 654, 657 and 659).

After block 670, the routine continues to block 685 to determine if anyrouting paths for inter-node communications are affected by theindication received in block 605, such as based on the determinationwith respect to block 660. If so, the routine continues to block 687,and otherwise continues to block 689. In block 687, the routinedetermines a new destination substrate network address to use for eachdestination computing node in an affected routing path for inter-nodecommunications for one or more sending computing nodes, in a mannersimilar to that discussed with respect to block 625 and elsewhere. Theroutine then stores the determined new information as part of thenetwork topology information for the managed computer network. Afterblock 687, or if the routine determines in block 685 that there are notany affected paths, the routine continues to block 689 to optionallyupdate the mapping information stored by one or more communicationmanager modules affected by changes that result from the indicationreceived in block 605, such as one or more routing path changes and/orone or more changes to configured network topology and accessiblecomputing nodes based on connection of a managed computer network to avirtual peering router. In addition, in block 689, the routineoptionally initiates the sending of one or more routing-relatedcommunications to one or more managed computer networks (e.g., tocomputing nodes of those managed computer networks that participate in arouting protocol for those managed computer networks), such as toreflect routing changes corresponding to a connection of an indicatedmanaged computer network to a virtual peering router, or to indicateother routing information.

If it is instead determined in block 610 that a message of another typeis received, the routine continues to block 690 to perform anotherindicated operation as appropriate. For example, as discussed in greaterdetail elsewhere, in some embodiments the routine may generate and sendrouting information to at least some computing nodes of a managedcomputer network that participate in a routing protocol for that managedcomputer network, including in a manner that is specific to the contextof the recipient computing node within the configured network topologyof the managed computer network, and/or in a manner to coordinate therouting information provided to the various computing nodes. Thegeneration and sending of such routing information may be initiated invarious manners, such as based on received routing information and/orother updates to configured network topology information (e.g., asdiscussed with respect to block 689), in a periodic manner, etc. Inaddition, in embodiments in which clients pay fees for various types offunctionality provided to them, such as fees for connecting to virtualpeering routers and/or for at least some routing-related communicationsthat are received or sent, the routine may further track correspondingoperations and provide such information to the system manager module(e.g., periodically, as soon as usage occurs, etc.).

After blocks 689 or 690, or if it is determined in block 635 that thereare no more computing nodes, the routine continues to block 695 todetermine whether to continue, such as until an explicit indication toterminate is received. If it is determined to continue, the routinereturns to block 605, and if not continues to block 699 and ends.

In addition, various embodiments may provide mechanisms for customer orother client users and other entities to interact with an embodiment ofthe system manager module for purpose of configuring computing nodes andtheir communications. For example, some embodiments may provide aninteractive console (e.g. a client application program providing aninteractive user interface, a Web browser-based interface, etc.) fromwhich users can manage the creation or deletion of virtual computernetworks, and the configuration of network topology information forvirtual computer networks (including connection to and other use ofvirtual peering routers), as well as more general administrativefunctions related to the operation and management of hosted applications(e.g., the creation or modification of user accounts; the provision ofnew applications; the initiation, termination, or monitoring of hostedapplications; the assignment of applications to groups; the reservationof time or other system resources; etc.). In some embodiments, some orall of the functionality of an embodiment of the CNS system may beprovided in exchange for fees from users or other entities acting ascustomers or other clients of the CNS system, as discussed previously,and if so the mechanisms for such clients to interact with an embodimentof the system manager module may include mechanisms for users and otherentities to provide payment and payment-related information, as well asto monitor corresponding payment information, and the CNS system maytake various actions to obtain appropriate payments from such clients.In addition, some embodiments may provide an API that allows othercomputing systems and programs to programmatically invoke at least someof the described functionality, such as APIs provided by libraries orclass interfaces (e.g., to be invoked by programs written in C, C++, orJava) or otherwise, and/or using network service protocols such as viaWeb services. Additional details related to the operation of exampleembodiments of a program execution service and/or configurable networkservice with which the described techniques may be used are available inU.S. application Ser. No. 11/394,595, filed Mar. 31, 2006 and entitled“Managing Communications Between Computing Nodes;” U.S. application Ser.No. 11/395,463, filed Mar. 31, 2006 and entitled “Managing Execution ofPrograms by Multiple Computing Systems;” U.S. application Ser. No.11/692,038, filed Mar. 27, 2007 and entitled “ConfiguringIntercommunications Between Computing Nodes;” and U.S. application Ser.No. 12/332,214, filed Dec. 10, 2008 and entitled “Providing Access ToConfigurable Private Computer Networks;” each of which is incorporatedherein by reference in its entirety. In addition, additional detailsrelated to the management of provided virtual networks that may be usedby at least some embodiments of a CNS system, such as in conjunctionwith an Overlay Network Manager module of such a CNS system, areavailable in U.S. application Ser. No. 12/060,074, filed Mar. 31, 2008and entitled “Configuring Communications Between Computing Nodes;” inU.S. application Ser. No. 12/414,260, filed Mar. 30, 2009 and entitled“Providing Logical Networking Functionality For Managed ComputerNetworks;” and in U.S. application Ser. No. 12/491,818, filed Jun. 25,2009 and entitled “Providing Virtual Networking Functionality ForManaged Computer Networks;” each of which is also incorporated herein byreference in its entirety.

It will also be appreciated that, although in some embodiments thedescribed techniques are employed in the context of a data centerhousing multiple physical machines hosting virtual machines, otherimplementation scenarios are also possible. For example, the describedtechniques may be employed in the context an organization-wide networkor networks operated by a business or other institution (e.g. auniversity) for the benefit of its employees and/or members.Alternatively, the described techniques could be employed by a networkservice provider to improve network security, availability, andisolation. In addition, example embodiments may be employed within adata center or other context for a variety of purposes. For example,data center operators or users that sell access to hosted applicationsto customers may in some embodiments use the described techniques toprovide network isolation between their customers' applications anddata; software development teams may in some embodiments use thedescribed techniques to provide network isolation between variousenvironments that they use (e.g., development, build, test, deployment,production, etc.); organizations may in some embodiments use thedescribed techniques to isolate the computing resources utilized by onepersonnel group or department (e.g., human resources) from the computingresources utilized by another personnel group or department (e.g.,accounting); or data center operators or users that are deploying amulti-component application (e.g., a multi-tiered business application)may in some embodiments use the described techniques to providefunctional decomposition and/or isolation for the various componenttypes (e.g., Web front-ends, database servers, business rules engines,etc.). More generally, the described techniques may be used tovirtualize physical networks to reflect almost any situation that wouldconventionally necessitate physical partitioning of distinct computingsystems and/or networks.

It will also be appreciated that in some embodiments the functionalityprovided by the routines discussed above may be provided in alternativeways, such as being split among more routines or consolidated into fewerroutines. Similarly, in some embodiments illustrated routines mayprovide more or less functionality than is described, such as when otherillustrated routines instead lack or include such functionalityrespectively, or when the amount of functionality that is provided isaltered. In addition, while various operations may be illustrated asbeing performed in a particular manner (e.g., in serial or in parallel)and/or in a particular order, those skilled in the art will appreciatethat in other embodiments the operations may be performed in otherorders and in other manners. Those skilled in the art will alsoappreciate that the data structures discussed above may be structured indifferent manners, such as by having a single data structure split intomultiple data structures or by having multiple data structuresconsolidated into a single data structure. Similarly, in someembodiments illustrated data structures may store more or lessinformation than is described, such as when other illustrated datastructures instead lack or include such information respectively, orwhen the amount or types of information that is stored is altered.

From the foregoing it will be appreciated that, although specificembodiments have been described herein for purposes of illustration,various modifications may be made without deviating from the spirit andscope of the invention. Accordingly, the invention is not limited exceptas by the appended claims and the elements recited therein. In addition,while certain aspects of the invention are presented below in certainclaim forms, the inventors contemplate the various aspects of theinvention in any available claim form. For example, while only someaspects of the invention may currently be recited as being embodied in acomputer-readable medium, other aspects may likewise be so embodied.

1-2. (canceled)
 3. A computer-implemented method comprising: undercontrol of one or more computing systems of a configurable networkservice that provides virtual computer networks to clients, receivingone or more first requests to provide a first virtual computer networkfor a first client in accordance with specified first configurationinformation, the first configuration information indicating one or morespecified first networking devices of the first virtual computer networkthat interconnect multiple first computing nodes of the first virtualcomputer network; receiving one or more second requests to provide asecond virtual computer network for a second client in accordance withspecified second configuration information, the second configurationinformation indicating one or more specified second networking devicesof the second virtual computer network that interconnect multiple secondcomputing nodes of the second virtual computer network; andautomatically providing the first virtual computer network in accordancewith the first configuration information and automatically providing thesecond virtual computer network in accordance with the secondconfiguration information, the providing of the first and second virtualcomputer networks including overlaying the first and second virtualcomputer networks on a distinct substrate network without physicallyproviding the one or more first networking devices and withoutphysically providing the one or more second networking devices, theautomatic providing of the first and second virtual computer networksfurther including: in response to an instruction from the first client,establishing a first logical connection between at least one of thefirst networking devices of the first virtual computer network and apeering router that enables interactions with one or more other computernetworks; in response to an instruction from the second client,establishing a second logical connection between at least one of thesecond networking devices of the second virtual computer network and thepeering router; and forwarding a plurality of communications over thesubstrate network that are each sent from one of the first and secondcomputing nodes and that are each delivered to at least one of the firstand second computing nodes, the forwarding of the plurality ofcommunications including forwarding multiple communications between thefirst and second virtual computer networks via the established first andsecond logical connections without physically providing the peeringrouter, the forwarding of the multiple communications being performed ina manner that emulates functionality that would be provided by thepeering router if the peering router was physically provided.
 4. Themethod of claim 3 wherein the peering router is a virtual peeringrouter, wherein the establishing of the first and second logicalconnections includes facilitating configurations that enable themultiple first computing nodes of the first virtual computer network todirect communications to the multiple second computing nodes of thesecond virtual computer network, and wherein the forwarded multiplecommunications are each forwarded from one of the multiple firstcomputing nodes to at least one of the multiple second computing nodes.5. The method of claim 4 wherein the facilitating of the configurationsis performed in accordance with peering configuration informationsupplied by the first client for the peering router and includesconfiguring one or more modules of the configurable network service. 6.The method of claim 5 wherein the peering configuration informationprevents communications from any virtual computer networks to be sent tothe first computing nodes of the first virtual computer network via thepeering router.
 7. The method of claim 5 wherein the peeringconfiguration information indicates one or more filters to limitcommunications that are allowed to be sent to the first computing nodesof the first virtual computer network via the peering router from othervirtual computer networks.
 8. The method of claim 5 wherein theinstruction from the first client and the peering configurationinformation are supplied as part of the received one or more firstrequests.
 9. The method of claim 5 wherein the instruction from thefirst client further indicates to create the peering router on behalf ofthe first client, and wherein the providing of the first and secondvirtual computer networks further includes providing functionality toemulate functionality of the peering router.
 10. The method of claim 4further comprising establishing third logical connections from one ormore third virtual computer networks to the peering router, theestablishing of the third logical connections including performingconfigurations to enable the multiple first computing nodes of the firstvirtual computer network to direct communications to multiple thirdcomputing nodes of the one or more third virtual computer networks, toenable the multiple third computing nodes of the one or more thirdvirtual computer networks to direct communications to the multiple firstcomputing nodes of the first virtual computer network and to themultiple second computing nodes of the second virtual computer network,and wherein the forwarding of the plurality of communications furtherincludes forwarding multiple additional communications that are eachbetween at least two of the first, second and third virtual computernetworks.
 11. The method of claim 4 wherein the establishing of thefirst and second logical connections further includes performingadditional configurations to enable the multiple second computing nodesof the second virtual computer network to direct communications to themultiple first computing nodes of the first virtual computer network.12. The method of claim 11 wherein the additional configurations areperformed in accordance with additional peering configurationinformation supplied by the second client for the peering router, theadditional peering configuration information indicating one or morefilters to limit communications that are allowed to be sent to thesecond computing nodes of the second virtual computer network via thepeering router from the first virtual computer network.
 13. The methodof claim 4 wherein the automatic providing of the first and secondvirtual computer networks further includes: receiving one or morerouting communications via the established first and second logicalconnections that are directed to the virtual peering router and includenetwork routing information for at least one of the first and secondvirtual computer networks, the one or more routing communications beingspecified in accordance with one or more predefined network routingprotocols and being sent by at least one of the multiple first andsecond computing nodes; and using the network routing informationincluded in the received one or more routing communications as part ofthe facilitating of the configurations that enable the multiple firstcomputing nodes of the first virtual computer network to directcommunications to the multiple second computing nodes of the secondvirtual computer network.
 14. The method of claim 13 wherein the networkrouting information included in the received one or more routingcommunications is from the second computer network and indicates atleast some of the multiple second computing nodes, wherein the computingnodes to which the multiple communications are forwarded are one or moreof the at least some second computing nodes, and wherein the receivingof the one or more routing communications includes intercepting the oneor more routing communications before the one or more routingcommunications are forwarded over the substrate network, and inhibitingforwarding of the intercepted routing communications to the virtualpeering router.
 15. The method of claim 4 wherein the establishing ofthe first and second logical connections includes sending one or morerouting communications to the first computer network that includesrouting information about at least some of the multiple second computingnodes, and wherein the computing nodes to which the multiplecommunications are forwarded are one or more of the at least some secondcomputing nodes.
 16. The method of claim 3 wherein the forwarding of theplurality of communications includes: forwarding multiple firstcommunications for the first virtual computer network between themultiple first computing nodes over the substrate network in a mannerthat emulates functionality that would be provided by the one or morefirst networking devices if the one or more first networking deviceswere physically provided; and forwarding multiple second communicationsfor the second virtual computer network between the multiple secondcomputing nodes over the substrate network in a manner that emulatesfunctionality that would be provided by the one or more secondnetworking devices if the one or more second networking devices werephysically provided.
 17. The method of claim 16 wherein the configurablenetwork service provides a plurality of computing nodes for use inprovided virtual computer networks, wherein the multiple first computingnodes and the multiple second computing nodes are each a distinct subsetof the plurality of computing nodes, wherein the configurable networkservice provides multiple modules that manage the multiple first andsecond communications by modifying outgoing communications from sendingcomputing nodes to be encoded with information specific to the substratenetwork before transmission over the substrate network and by modifyingincoming communications to destination computing nodes to remove theencoded information specific to the substrate network after thetransmission over the substrate network.
 18. The method of claim 3wherein the multiple first computing nodes are each a virtual machinehosted on one of multiple physical computing systems of the configurablenetwork service, wherein the providing of the first virtual computernetwork includes configuring one or more virtual machine communicationmanager modules that execute on one or more of the physical computingsystems to manage communications for the hosted virtual machines, andwherein the establishing of the first logical connection and theforwarding of the multiple communications are performed dynamicallywhile the first virtual computer network is operational and withoutstopping use of the first virtual computer network based at least inpart on management of communications by the virtual machinecommunication manager modules.
 19. A computer-readable storage mediumwhose contents configure a computing system to perform a method, themethod comprising: under control of the configured computing system,receiving information from a first client for use in configuring a firstvirtual computer network for the first client, the configuring includingspecifying inter-connections between multiple first computing nodes ofthe first virtual computer network, the configuring further includingspecifying a first connection between the multiple first computing nodesand a virtual peering router that enables interactions with one or moreother second virtual computer networks; and automatically providing theconfigured first virtual computer network in accordance with theconfiguring by overlaying the first virtual computer network on adistinct substrate network, the providing of the first virtual computernetwork including: establishing the first connection between the firstvirtual computer network and the virtual peering router; and after theone or more second virtual computer networks have established one ormore second connections to the virtual peering router, the one or moresecond virtual computer networks having multiple second computing nodes,forwarding a plurality of communications over the substrate network thatare each sent from one of the first and second computing nodes and thatare each delivered to at least one of the first and second computingnodes, the forwarding of the plurality of communications includingforwarding multiple communications between the first virtual computernetwork and the one or more second virtual computer networks via theestablished first and second connections without physically providingthe virtual peering router. 20-22. (canceled)
 23. A computing system,comprising: one or more processors; and a manager module that isconfigured to, when executed by at least one of the processors: receivefirst configuration information from a first client to configure a firstcomputer network provided for use by the first client, the firstconfiguration information indicating inter-connections between multiplefirst computing nodes of the provided first computer network thatinclude one or more first networking devices; receive secondconfiguration information from a second client to configure a secondcomputer network provided for use by the second client, the secondconfiguration information indicating inter-connections between multiplesecond computing nodes of the provided second computer network thatinclude one or more second networking devices; automatically configurethe provided first computer network for the first client in accordancewith the received first configuration information and automaticallyconfigure the provided second computer network for the second client inaccordance with the received second configuration information, theconfiguring of the provided first and second computer networks includingoverlaying each of the provided first and second computer networks on adistinct third computer network without physically providing the one ormore first networking devices and without physically providing the oneor more second networking devices, the multiple first and secondcomputing nodes being connected to the third computer network; forwardmultiple communications between the multiple first computing nodes overthe third computer network without physically providing the one or morefirst networking devices, and forward multiple other communicationsbetween the multiple second computing nodes over the third computernetwork without physically providing the one or more second networkingdevices; in response to a request from at least one of the first andsecond clients, establish a logical inter-connection between theprovided first and second computer networks to enable communicationsbetween the multiple first computing nodes and the multiple secondcomputing nodes in accordance with specified configuration informationfor the logical inter-connection; and forward multiple additionalcommunications over the third computer network between the first andsecond computer networks via the established logical inter-connection inaccordance with the specified configuration information.
 24. Thecomputing system of claim 23 wherein the third computer network is asubstrate network, wherein the provided first and second computernetworks are each virtual computer networks overlaid on the substratenetwork, wherein the manager module is part of a configurable networkservice and provides an interface for use by the first and secondclients to configure the provided first and second virtual computernetworks, wherein the multiple computing nodes of each of the providedfirst and second computer networks are a subset of a plurality ofcomputing nodes provided by the configurable network service for usewith the provided first and second computer networks, wherein theestablishing of the logical inter-connection between the provided firstand second computer networks includes establishing a first logicalconnection from at least one of the first networking devices to avirtual peering router and includes establishing a second logicalconnection from at least one of the second networking devices to thevirtual peering router, the virtual peering router not being physicallyprovided, and wherein the forwarding of the multiple additionalcommunications between the first and second virtual computer networksincludes emulating functionality that would be provided by the virtualpeering router if the virtual peering router was physically provided.25. The computing system of claim 23 wherein the establishing of thelogical inter-connection between the provided first and second computernetworks includes establishing a first logical connection from at leastone of the first networking devices to a first virtual peering routerand includes establishing a second logical connection from at least oneof the second networking devices to a second virtual peering router, thefirst and second virtual peering routers not being physically providedand being logically connected to each other. 26-27. (canceled)